
No. 9044 










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Bureau of Mines Information Circular/1985 




Molybdenum Availability- 
Market Economy Countries 

A Minerals Availability Appraisal 

By C. M. Palencia 




UNITED STATES DEPARTMENT OF THE INTERIOR 



7® 

V/NES 75TH A*»^ 



Information Circular 9044 

Molybdenum Availability- 
Market Economy Countries 

A Minerals Availability Appraisal 

By C. M. Palencia 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



As the Nation's principal conservation agency, the Department of the 
Interior has responsibility for most of our nationally owned public lands 
and natural resources. This includes fostering the wisest use of our land 
and water resources, protecting our fish and wildlife, preserving the 
environmental and cultural values of our national parks and historical 
places, and providing for the enjoyment of life through outdoor recreation. 
The Department assesses our energy and mineral resources and works to 
assure that their development is in the best interests of all our people. The 
Department also has a major responsibility for American Indian reserva- 
tion communities and for people who live in island territories under U.S. 
administration. 






Library of Congress Cataloging in Publication Data 



Palencia, Cesar M. 

Molybdenum availability — market economy countries. 

(Bureau of Mines information circular; 9044) 

Bibliography: p. 21 

Supt. of Docs, no.: I 28.27: 

1. Molybdenum industry 2. Molybdenum mines and mining. I. United States. Bureau of Mines. FJ. Tide. 
IE. Series: Information circular (United States. Bureau of Mines); 9044. 



TN295:U4~ 



HD9539.M62 



622 s 



338.2 '74646 



85-600115 



For sale by the Superintendent of Documents, U.S. Government Printing Office 
Washington, DC 20402 



Ill 



PREFACE 



The Bureau of Mines is assessing the worldwide availability of critical minerals, ex- 
clusive of the energy fuel minerals. The Bureau identifies, collects, compiles, and evaluates 
specific information on producing, developing, and explored mines and deposits, including 
the processing plants that convert raw minerals to marketable products. The objectives 
are to classify domestic and foreign resources in order to identify by cost evaluation those 
that are reserves, and to prepare analyses of the availability of these minerals at different 
times and conditions. 

This report on the availability of molybdenum is part of a continuing series of reports 
that analyze the availability of critical minerals from domestic and foreign sources. Analyses 
of other minerals are currently in progress. Questions about these reports should be ad- 
dressed to Chief, Division of Minerals Availability, Bureau of Mines, 2401 E St., NW., 
Washington DC 20241. 









CONTENTS 

Page Page 

Preface iii Other processing 10 

Abstract 1 Deposit evaluation procedure 10 

Introduction 2 Assumptions 10 

Molybdenum products and uses 2 Cost estimation 12 

Marketing- and pricing structure 3 Operating costs 12 

World production, consumption, and trade 4 Capital costs 13 

U.S. production, consumption, and trade 5 Molybdenum availability 14 

Geology 6 Evaluation methodology 14 

Mineralogy 6 Total availability 14 

Resources 7 Annual availability 16 

Primary molybdenum resources 8 Byproduct molybdenum total availability 17 

Byproduct molybdenum resources 9 Conclusions 20 

Mining and processing technology 9 References 21 

Mining methods 9 Appendix. -Deposit descriptions for primary 

Beneficiation 9 molybdenum 23 

ILLUSTRATIONS 

1. Molybdenum consumption according to industrial use, market economy countries, 1983 2 

2. Molybdenum deposit locations, market economy countries , 7 

3. Minerals Availability program evaluation workflow 11 

4. Mineral resource classification categories 11 

5. Total molybdenum available from primary deposits, market economy countries 15 

6. Total molybdenum available from producing mines at a 0-pct DCFROR, market economy countries 15 

7. Total molybdenum potentially available in the United States and Canada from producing mines and nonpro- 
ducing deposits 16 

8. Potential annual production of molybdenum from producing mines and nonproducing deposits at various 

cost ranges, market economy countries 17 

9. Potential annual production of molybdenum from developing and explored deposits at various cost ranges, market 
economy countries 18 

10. Total available molybdenum byproducts from copper deposits, market economy countries 18 

11. Potential annual capacity of molybdenum byproducts at selected copper prices, market economy countries . . 19 

TABLES 

1. Comparative prices of molybdenum products 3 

2. Molybdenum production from market economy and centrally planned economy countries 4 

3. Molybdenum consumption from production in market economy countries 4 

4. U.S. import duties on molybdenum materials 5 

5. U.S. salient molybdenum concentrate statistics 5 

6. U.S. molybdenum exports as reported by producers 5 

7. Physical and chemical properties of principal molybdenum minerals 6 

8. Primary molybdenum deposits and in situ demonstrated resources, market economy countries, January 1983 8 

9. Byproduct molybdenum deposits and in situ demonstrated resources, market economy countries, January 1983 8 

10. Byproduct commodity prices, market economy countries, January 1983 12 

11. Estimated cost of mining and milling operations from primary producers in the United States and Canada, 
January 1983 13 

12. Estimated mine and mill operating costs for primary molybdenum producers in the United States and Canada, 
January 1983 13 

13. Estimated capital costs for developing and explored molybdenum deposits, market economy countries, 
January 1983 14 

14. Molybdenum potentially available from primary producing, developing, and explored deposits in market 
economy countries at selected 1983 prices, at a 15-pct DCFROR 14 

'olybdenum potentially available within the United States and Canada, at a 15-pct DCFROR 16 

16. Potential 1983 molybdenum production capacities from primary molybdenum mines and deposits in market 
economy countries, at a 15-pct DCFROR 17 

17. Total molvbdenum byproduct potentially available in market economy countries at selected copper production costs, 

at a 15-pct DCFROR 19 

18. Annual U.S. molybdenum byproduct capacity and demonstrated resources of recoverable molybdenum from 
evaluated U.S. copper operations at selected copper prices, at a 15-pct DCFROR 19 



VI 

CONTENTS— Continued 

TABLES— Continued 

Page 

19. Molybdenum byproduct potential annual production for 1983 and 1991 from market economy countries, at a 
15-pct DCFROR 19 

20. Estimated total 1983 molybdenum capacity from primary and byproduct producers in market economy 
countries 20 









UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 



op 


degree Fahrenheit 


mm 


millimeter 


h 


hour 


mt 


metric ton 


in 


inch 


mt/d 


metric ton per day 


km 


kilometer 


mt/yr 


metric ton per year 


lb 


pound 


pet 


percent 


Ib/yr 


pound per year 


ppm 


part per million 


m 


meter 


yr 


year 



MOLYBDENUM AVAILABILITY— MARKET ECONOMY COUNTRIES 

A Minerals Availability Appraisal 

By C. M. Palencia 1 



ABSTRACT 



The Bureau of Mines evaluated the potential availability of molybdenum resources 
from 88 mines and deposits that account for more than 90 pet of the demonstrated resource 
base in market economy countries (MEC's). For each property, tonnage-cost relationships 
were developed that indicate the molybdenum potentially available at different average 
production costs, including a 15-pct rate of return on invested capital. From the 23 MEC 
primary deposits, 2.5 billion lb Mo was determined to be potentially available at a price 
of S4/lb, rising to 4.7 billion lb Mo at $8/lb. 

Copper price-molybdenum tonnage relationships were developed for those mines and 
deposits from which molybdenum can be recovered as a byproduct of copper production. 
This analysis showed that another 3.4 billion lb Mo is potentially available based on a cop- 
per price of $0.75/lb. rising to 4.3 billion lb Mo at $1.00/lb. 

The United States has been the world's largest molybdenum supplier since 1924. Its 
remaining resources are sufficient to meet the domestic demand of 57 million lb/yr Mo 
(averaged for a 10-yr period) through the end of the century. Production from primary 
domestic mines was suspended during most of 1983 because of oversupply of materials. 
A major concern is the cheap molybdenum byproducts from foreign copper operations 
in which employment and the need for hard currency override economics in meeting pro- 
duction goals. 

PhysicaJ scientist (mining engineer). Minerals Availability Field Office, Bureau of Mines, Denver, CO. 



INTRODUCTION 



This study provides analyses of the resources, engineer- 
ing, economics, and other factors that influence the availabili- 
ty of molybdenum. Production costs, including mining and 
beneficiation, were determined for each property. Since some 
producers market molybdenite concentrate as a final product 
at the minesite, no attempt was made to analyze factors af- 
fecting the availability beyond that point. 

The molybdenum resources located in the Soviet Union, 
China, and other centrally planned economy countries 
(CPEC's) were not analyzed in this study. Inasmuch as it is 



difficult to collect quantitative resource information and pro- 
duction cost estimates from these countries, reliable and 
definitive estimates could not be developed. 

Domestic deposits were evaluated by personnel of the 
Bureau's Field Operations Centers, and foreign data collec- 
tion and cost estimation were performed under contract by 
Pincock, Allen and Holt Inc., Tucson, AZ; personnel of the 
Bureau's Minerals Availability Field Office, Denver, CO, 
evaluated the data and performed the economic evaluation 
analyses. 



MOLYBDENUM PRODUCTS AND USES 



A rare metallic element, molybdenum is gaining import- 
ance in industrial applications. In a pure state, molybdenum 
is a lustrous gray metal with a melting temperature of 4,730° 
F. The word molybdenum came from the ancient Greek word 
Molybdos, which means "leadlike," a name applied to all 
minerals that were soft and leadlike in character, probably 
minerals such as molybdenite, galena, and graphite. In 1778, 
Karl Wilhelm Scheele differentiated molybdenite from the 
other soft minerals. Four years later, J. J. Hjelm isolated the 
metal as a new element now known as molybdenum ("moly" 
for short). 

It took more than a century to find a use for the new 
element. The French first applied molybdenum to toughen 
steel used in armor plates. Later the Germans improved the 



technology by using molybdenum as an alloying element with 
other metals. Further research found more applications for 
molybdenum including lubricants, paints, pigments, fertilizer 
additives, chemical catalysts, vitamin supplements, flame 
retardants, smoke suppressants, refractory metals, and 
semiconductor applications. 

In spite of these diverse uses, 83 pet of molybdenum con- 
sumption is for alloying uses. In some stainless steels, 
molybdenum tends to minimize surface and intergranular cor- 
rosion. Figure 1 shows an approximate percentage consump- 
tion in market economy countries (MEC's) according to use 
for 1983 (l) 2 . 

2 Italicized numbers in parentheses refer to items in the list of references 
preceding the appendix. 




KEY 
Alloying uses 



Super and special alloys 
3 pet 



Molybdenum metal 
Other uses/ 6 pet 

pet 
Figure 1— Molybdenum consumption according to industrial use, market economy countries, 1983. 



Basically, nonintegrated mine operations (mostly small 
and byproduct producers) sell molybdenum in concentrate 
form to independent companies for roasting. The major por- 
tion of the total concentrate production is roasted to technical- 
grade molybdenum trioxide (MoOj), the intermediate 
marketable material from which almost all molybdenum prod- 
ucts are made; a small portion of the concentrate is used 



directly in mineral form (MoS,). Any technical-grade oxide 
not directly used in the industry is further processed into 
another marketable form; i.e.. high-purity MoO, and fer- 
romolybdenum. The high-purity MoO, in turn is converted 
either into chemical form (as pure salts), metal form, or alloy 
form (as master alloys for high-temperature metals). 



MARKETING AND PRICING STRUCTURE 



There are two price structures in molybdenum markets, 
the producers' price and the dealers* price. Molybdenum 
marketed directly by producers is sold at the producers' price. 
Normally, this accounts for about 90 pet of total molybdenum 
production. The remainder is sold at a dealers' price in the 
open market: this often commands a premium in times of 
tight supply hut sells at a discount in times of plenty. In 1979. 
when molybdenum demand was high and supply was tight. 
the dealers' price went up to more than twice the producers' 
price. However, when demand softened from mid- 1980 
through 1981. the dealers' price went down to as much as 
S3/lb below the producers' price. Table 1 provides price com- 
parisons for the various forms of molvbdenum from 1975 to 
1983. 

Molybdenum on the domestic market is almost all sold 
in processed forms: i.e.. oxides, ferro molybdenum, and am- 
monium and sodium molybdate. Molybdenite (molybdenum 
sulfide in concentrate), if any. is sold in very small quantities 
for special uses such as lubricants. However, because of pro- 
tective tariffs on processed molybdenum products, the 
molybdenum market overseas, especially in Western Euro- 
pean countries, is mostly in the form of molybdenite concen- 
trates. While the United Kingdom, France, Italy, and West 
Germany, for example, have no tariffs on molybdenite, they 
impose 25 pet. 9 pet, 7.5 pet, and 7 pet tariffs, respectively, 
on ferromolybdenum (2). 

With the exception of 1977, molybdenum consumption 
in MEC's exceeded its production from 1974 through 1979. 
Consumption started declining in 1980 owing to the effects 
of the recession. In 1974. consumption exceeded production 
by about 42 million lb Mo. To offset demand requirements, 
the General Services Administration (GSA) released 35 
million lb from the U.S. Government Stockpile (3). With 
strong demand continuing in September 1976 the GSA re- 



leased all the remaining molybdenum concentrate from the 
Stockpile (4). The continued increase in consumption in 1978 
and 1979. which far exceeded production, forced a drawdown 
from producers' inventories. This expanded industrial de- 
mand, combined with the supply shortage situation caused 
by labor strikes in Canada and reduced molybdenum 
byproduct recovery from copper production, resulted in an 
artificially high price in 1979 and early 1980, especially in 
the international market. A self-imposed, anti-inflationary 
measure instituted by the major domestic producers during 
these years kept domestic molybdenum prices well below 
those of exported products. (See table 1.) As production in- 
creased and consumption dropped in late 1980, the supply- 
demand picture took a reverse trend. 

During the first quarter of 1981, while producers held 
the prices for technical molybdic oxides and ferromolybdenum 
at $9.70 to $9.35 and $10.60 to $10.25 per pound of contained 
molybdenum, respectively, dealers were selling the metal for 
about $1.25/lb lower. The price gap widened to about $3/lb 
in the last quarter (5). This price difference caused the pro- 
ducers to follow the downward trend, and in December 1981 
Codelco (the Government-owned Chilean copper producer) 
posted a price per pound of $5.55 for oxide and $6.55 for fer- 
romolybdenum. In early 1982, a wide difference in prices 
existed between individual producers. While Climax held to 
its published price of $8.75 for canned oxide, $9.90 for fer- 
romolybdenum, and $8.80 for briquettes, Codelco posted 
prices of $5.52 for oxide, $6.57 for ferromolybdenum, and 
$5.61 for briquettes. At the same time, Duval and Noranda 
quoted export prices of $7.00 for oxides, $8.10 for fer- 
romolybdenum, and $7.11 for briquettes. Dealers' prices for 
this period ranged from $4.80 to $5.15 for oxide and $5.15 
to $5.50 for ferromolybdenum. In September 1982, Climax 
firmed the price at $5.85 for oxide, $6.75 for fer- 



Table 1.— Comparative prices of molybdenum products 

(Dollars per pound of contained molybdenum) 



Concentrates 



Technical-grade oxide 



Ferromolybdenum 



Year Byproduct Climax Climax' Dealers 

1975 $ 2.20- S2.62 $2.62 $2.90 $2.90- $2.95 

1976 2.85- 3.20 2.70 3.54 3.30- 3.35 

1977 3.85- 4.01 4.01 4.31 3.60- 3.75 

1978 4.50- 5.15 4.95 5.30 9.00- 9.50 

1979 25 00 27.00 8.84 9.80 26.00-28.00 

1980 7.50 9.00 9.20 9.70 6.95- 7.45 

1981 5.80 7.90 7.90 8.50 6.65- 6.25 

1982 3.10 3.50 7.90 8.50 4.30- 4.60 

1983 3.3Q 3.60 (J) (j) 3.75- 4.05 

The Climax oxide prices shown are for domestic consumption. The oxide export prices were as follows 

1980 . . . .$21.50-522.49 1982 . . . .511.15-513.23 

1981 . . . .$18.50-519.29 1983 ... .5 8.65-513.23 
'Suspended 

Source Metals Week, various years. 



Climax 
lump 



Dealers' 
export 



$3.44 


$3.45- 


$3.50 


4.10 


3.80- 


3.90 


4.99 


5.40- 


5.80 


6.10 


9.75- 


10.00 


6.68 


29.00- 


29.50 


9.90 


8.60- 


9.30 


9.40 


7.30- 


8.00 


9.40 


5.35- 


5.55 


P) 


4.45- 


4.55 



romolybdenum, and $5.96 for briquettes. Simultaneously, 
Codelco lowered its price for oxide to $4.50/lb, while the 
dealers sold the material for as low as $2.50/lb (6). 

In December 1982, the average dealers' price for oxide 
slipped to $2.47/lb Mo. Low price, compounded by high in- 
ventory and sluggish demand for the metal, caused primary 
producers to stop mine production for most of 1983; the only 



new molybdenite supply at the time came from byproduct 
producers. This limited supply of molybdenite induced the 
drawdown of inventories and eventually resulted in an up- 
turn of price. Although there was no reported producers' price 
in 1983, dealers' price for oxide ranged from $3.75/lb to 
$4.05/lb Mo for most of the year (1). 



WORLD PRODUCTION, CONSUMPTION, AND TRADE 



Since the reopening of the Climax Mine in 1924, the 
United States has maintained its position as the world's 
largest molybdenum producer. A net exporter, the United 
States supplies not only MEC's, but also CPEC's. 
Molybdenum production in MEC's over the last 10 yr aver- 
aged 178 million lb, with the United States accounting for 
63 pet of the total, or 114 million lb/yr (table 2). Consump- 
tion from MEC production over the last 10 yr averaged 148 
million lb/yr with the United States using 57 million lb/yr 
(table 3). This indicates that more than half of U.S. produc- 
tion is exported, as is a large portion of the production from 
Canada and Chile. 

China, the U.S.S.R., and other CPEC's, as shown in table 
2, produced an estimated 34 million lb in 1982. Nevertheless, 
these countries as a whole are net importers of molybdenum. 



As a block these countries imported an average of 17 million 
lb/yr from 1974 through 1982 (table 3). 

International trade is primarily limited to molybdenite, 
especially in Western European countries because of protec- 
tive tafiffs imposed on processed molybdenum forms. In order 
to directly enter the European market, AMAX Inc. (the U.S.'s 
largest producer) established processing plants in the 
Netherlands, England, and Italy. 

Although molybdenum enters international trade in the 
form of molybdenite concentrate and various primary prod- 
ucts, prices are based on the molybdenum content of the prod- 
uct. Normally, molybdenite is marketed at a minimum grade 
of 90 pet MoS 2 ; however, molybdenum produced as a 
byproduct may be marketed at a lower MoS 2 grade. 

To protect domestic molybdenum producers, the United 






Table 2.— Molybdenum production from market economy and centrally planned economy countries 

(Million pounds of contained molybdenum) 

Country 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 

MEC's: 

United States 112 106 113 122 132 144 151 140 83 34 

Canada 29 32 31 33 31 25 26 31 31 23 

Chile 21 23 24 24 29 30 30 34 44 33 

Mexico ' 1 1 1 ' ' 1 1 11 13 

Peru 1 1 1 1 2 3 6 7 7 6 

Total 

CPEC's: 

China 

U.S.S.R 

Others 

Total 2 

Grand total 183 182 193 205 220 229 240 241 210 143 

p Prelimary. 
"Less than 170,000 lb. 

2 Bulgaria, Mongolia, Niger , North Korea, Romania, Turkey, and Yugoslavia are believed to have molybdenum production, but no quantitative out- 
put information is available. 
Sources: Engineering and Mining Journal and Bureau of Mines Mineral Industry Surveys, various years. 



163 


162 


169 


180 


194 


202 


213 


213 


176 


109 




20 






20 




3 

20 

1 


3 

21 

1 


4 
21 

1 


4 
22 

1 


4 

22 

1 


4 

23 

1 


4 

24 

6 


4 

24 

6 


20 


20 


24 


25 


26 


27 


27 


28 


34 


34 



Table 3.— Molybdenum consumption from production in market economy countries 

(Million pounds of contained molybdenum) 

1974 1975 1976 1977 1978 1979 1980 1981~ 

MEC's: 

United States 75 55 57 60 69 71 60 58 

Western Europe" 78 66 70 70 72 75 65 57 

Japan 27 21 25 24 25 25 28 26 

Subtotal 

CPEC's 6 

Other 

Subtotal 

Total 207 168 177 182 200 205 182 170 

e estimated. P preliminary. 

'Production data include both Government and private shipment and releases from inventory stockpile. 

Source: Engineering and Mining Journal, various years. 



1982 



1983 



34 


30 


55 


53 


26 


24 



180 


142 


152 


154 


166 


171 


153 


141 


115 


107 


14 
13 


15 
11 


15 
10 


17 
11 


22 
12 


22 
12 


18 
11 


18 
11 


15 
9 


18 
8 


27 


26 


25 


28 


34 


34 


29 


29 


24 


26 



139 



133 



States also imposed a restrictive tariff schedule on most 
molybdenum products, especially those coming from coun- 
tries not having a most-favored-nation (MFN) status. In 1979, 
a multilateral trade negotiation, known as the Tokyo Round, 
adopted new tariff agreements that placed most countries 
under the MFN status and gave them a much lower tariff 
rate. The agreement called for the phasing down of tariff 
rates for MFN countries over a 7-yr period ending in 1987 
(7). This two-tiered tariff schedule is shown in table 4. 



Table 4.— U.S. Import duties on molybdenum materials 

(Percent ad valorem, except where Indicated) 





Most-favored-nation (MFN) 


Non-MFN: 


Material 


Jan. 1, 1983 


Jan. 1, 1987 


Jan. 1983 


Ore and concentrate, c/lb. . 


10.5 


9.0 


35.0 


Material In chief value 








molybdenum . . . . «/lb . . 


8.0 


6.0 


50.0 


Plus pet ad valorem . . 


2.5 


1.9 


5.0 


Ferromolybdenum 


5.9 


4.5 


31.5 


Molybdenum: 








Waste and scrap 


8.3 


6.0 


50.0 


Wrought 


9.6 


6.6 


60.0 


Unwrought c/lb.. 


8.1 


6.3 


50.0 


Plus pet ad valorem 


2.5 


1.9 


15.0 


Molybdenum chemicals: 








Ammonium molybdate 


5.3 


4.3 


29.0 


Calcium molybdate . . 


4.8 


4.7 


24.5 


Molybdenum 








compounds 


3.7 


3.2 


20.5 


Potassium molybdate 


3.4 


3.0 


23.0 


Sodium molybdate . . . 


4.4 


3.7 


25.5 


Mixtures of inorganic 








compounds, chief 








value molybdenum . 


3.2 


2.8 


18.0 


Molybdenum orange . 


5.0 


5.0 


25.0 


Source: Blossom (7). 









U.S. PRODUCTION, CONSUMPTION, AND TRADE 



Table 5 shows production, shipments, and stocks of 
molybdenum in concentrate for U.S. producers. Shipments 
alone may not represent the actual mine production volume, 
since some molybdenum produced in a specific year may be 
shipped or released from the mine stockpile. The shipment 
statistics shown may be a little confusing; while the export 
figures are actual concentrate shipments to foreign countries, 
the domestic shipments of concentrate may not to used for 
domestic consumption per se. Domestic shipments, in part, 
represent deliveries of concentrate to intermediate processors 
or converters, who in turn may export finished molybdenum 
products. In addition, domestic consumption is not always 
the difference between the domestic production and foreign 
exports, since producers normally keep or release inventories 



depending on the status of supply and demand prevailing at 
the time. Total U.S. exports of molybdenum in all forms are 
shown in table 6. 

U.S. export destinations vary from year to year, though 
the major importing countries are the Netherlands, Japan, 
Belgian-Luxembourg, and the Federal Republic of Germany. 
Most of the concentrate exported is converted to oxides and 
reshipped to other countries, including CPEC's. 

Imports account for 2 to 5 pet of domestic U.S. consump- 
tion. The majority of imports are in the form of concentrate, 
primarily from Canada. Other sources of U.S. imports include 
China, a supplier of ammonium molybdate, Japan, Peru, and 
Western European countries. 



Table 5.— U.S. salient molybdenum concentrate statistics 

(Thousand pounds of contained molybdenum) 

Hem 1974 1975 1976 1977 1978 1979 1980 

Production 112,011 105,980 113,233 122,408 131,843 143,967 150,686 

Shipments': 

Domestic 3 78,198 68,552 83,592 95,308 99,511 107,099 114,285 

Export 39,965 36,618 30,935 29,666 31,183 36,405 35,026 

Stocks, mine and 

plant 18,659 10,680 9,390 9,161 8,980 9,520 18,101 

As reported by producers. 
'Part of domestic shipment is exported in molybdenum product forms. 



1981 



1982 



1983 



139,900 

86,182 
32,734 

35,548 



83,050 

55,918 
21,870 

35,527 



33,951 

39,822 
9,341 

36,407 



Table 6.— U.S. molybdenum exports as reported by producers 

(Thousand pounds of contained molybdenum) 



Item 


1974 


1975 


1976 


1977 


1978 


1979 


1980 


1981 


1982 


1983 


Molybdenite 

concentrate 
Molybdic oxide 
Others 


39,985 

35,949 

2,921 


36,618 

31,210 

1.874 


30,935 

29,644 

2,152 


29,666 

31,529 

1,803 


31,183 

33,258 

2,095 


36,405 

33,920 

1,853 


35,026 

33,167 

2,390 


32,734 

19,072 

932 


21,870 

22,938 

437 


9,341 

18,847 

839 


Total 


. 78,835 


69,702 


62,731 


62,998 


66,536 


72,178 


70,583 


52,738 


45,245 


29,027 



GEOLOGY 



Molybdenum deposits are classified into five genetic 
types: (1) primary porphyry or disseminated deposits, in- 
cluding stockworks and breccia pipes in which metallic 
sulfides are dispersed through relatively large volumes of 
altered and fractured rocks; (2) contact metamorphic zones 
and tactite bodies of silicated limestone adjacent to intrusive 
granitic rocks; (3) quartz veins; (4) pegmatites and aplite 
dikes; and (5) bedded deposits in sedimentary rocks (8). 

The first three genetic types are determined to be 
hydrothermal in origin. As such, nearly all resources in the 
world fall under these types. The remaining two types cur- 
rently do not possess any economic importance. Molybdenum 
from these types are recovered only when it interferes in the 
metallurgical recovery of the primary product (8). 

Primary porphyry deposits, the major source of 
molybdenite, occur as small disseminated grains in veins and 
veinlets of hydrothermally altered igneous rocks. The 
mineralization normally is associated with intrusions along 
fault intersections. Generally, the intrusive rocks are siliceous 
with composition ranging from granodiorite to granite. 

The average mineral concentration in the resources iden- 
tified for this study ranges from 0.1 to 0.5 pet MoS 2 . The 
major known deposits of this type are the Endako and Boss 
Mountain Mines of Canada, and the Climax, Henderson, and 
Mount Tolman deposits of the United States. 

Copper-molybdenum porphyry deposits are somewhat 
similar in origin to that of primary molybdenum porphyry 
deposits. The deposits are related to silicic intrusions and 
hydrothermal alteration. Molybdenite concentrations are 
much lower, ranging from 0.015 to 0.1 pet MoS 2 , and 
therefore can only be economically recovered as a byproduct 
(9). 

In contact-metamorphic and tactite deposits, molybdenite 
is widely distributed along the contact between granitic in- 
trusives and lime-rich sedimentary rocks. In many places, the 
size, shape, and occurrence of the ore bodies indicate that 
the mineralization was controlled by preore fracturing of the 
lime-rich host rock. The molybdenite is usually associated with 
scheelite, bismuthite, and copper sulfides. The deposits are 
generally small, but contain relatively high molybdenite con- 
centration, up to 0.6 pet MoS 2 . The only domestic molybdenite 
production from this type of depost was a byproduct from 
the Pine Creek tungsten mine in California (10). 

Molybdenite also occurs in fissure or quartz vein deposits. 



The vein filling is mainly quartz and molybdenite with minor 
amounts of pyrite, chalcopyrite, and chlorite and varies in 
size from a fraction of an inch to several feet. The mineral 
concentration also varies widely, and most of the molybdenite 
is fairly fine grained and appears to be concentrated along 
vein walls or joints and seams. The Questa surface mine in 
New Mexico is the only deposit known to have produced ap- 
preciable amounts of molybdenite from this type of deposit. 

Pegmatite and aplite dike deposits are igneous rocks that 
were formed by magmatic fluid filling dikes with rock com- 
position similar to that of the associated pluton. Molybdenite 
generally occurs in coarse crystalline structure, forming large 
rosettes and aggregates of flakes, which are valued as a 
mineral specimen rather than as a source of molybdenum. 
Mineralization normally occurs in small pods that give no 
leads to other pods and limit mining to single pods. Very few 
deposits of this type have been developed. Known deposits 
include the Val d'Or and Preissac deposits of Quebec, Canada 
(8). 

Molybdenite is also found in bedded sedimentary rocks 
like coal and shale, though the concentrations are too low 
to be of economic importance. In some lignitic sandstone 
deposits of Montana, the Dakotas, and Utah, the mineral ap- 
proaches economic concentrations. Some molybdenite 
minerals are also associated with bedded uranium in Arizona, 
Wyoming, South Dakota, New Mexico, and Utah. In such 
deposits, when the mineral reaches a high level of concen- 
tration, it becomes necessary to separate the molybdenite as 
it interferes with uranium recovery (9). 



MINERALOGY 

Molybdenum has not been found free or as a native metal 
in a natural environment. Even as a compound, it is relatively 
scarce, comprising only about 1.0 to 1.5 ppm concentration 
in the continental crust. This concentration is evenly 
distributed throughout igneous rocks, though higher concen- 
trations have been noted in basalt rocks. 

Molybdenite (MoS 2 ) and, to a minor extent, wulfenite 
(PbMo0 4 ), powellite [Ca(Mo,W)0 4 ], and ferrimolybdite 
[Fe 2 (Mo0 4 ) 3 .8H 2 0], are the most important minerals of 
molybdenum. Table 7 summarizes the physical and chemical 
properties of these principal minerals. Powellite and fer- 



Table 7.— Physical and chemical properties of principal molybdenum minerals (10) 



Properties 

Composition 

Mo pet . 

Crystal system 

Cleavage 

Sp.gr 

Color 

Tenacity 

Luster 

Fracture 

Hardness' 

Streak 



Molybdenite 



Wulfenite 



Powellite 



Ferrimolybdite 



MoS 2 

60.0 

Hexagonal 

Perfect in 1 direction 

4.6-4.7 

Lead-gray 



Flexible 
Metallic 



None 

1-1.5 

Bluish gray on paper, 
greenish on porcelain 
or glazed paper. 



PbMo0 4 

26.1 

Tetragonal 

Perfect in 4 directions . . 

6.5-7.0 

Grayish-white through 

yellow to orange and 

orange red. 

Brittle 

Adamantine or resinous 

Uneven 

3 

White 



Ca(Mo,W)0, 

39-48 

Tetragonal 

Indistinct 

4.3 

Straw yellow to dirty 
white. 

NA 



Subadamatine, pearly, or 
greasy. 

Uneven 

3.5-4 

White 



Fe 2 (Mo0 4 ) 3 .8H 2 0. 

39. 

Orthorombic. 

NA. 

2.99-4.5. 

Sulfur yellow. 



Powdery. 
Silky to earthy. 

None. 

1.5. 

Pale yellow. 



NA Not available. 
■Mohs scale. 



rimolybdite. which are products of oxidation from other 
minerals, have widespread occurrences, though it is unlike- 
ly that they will become major sources of molybdenum. 

Molybdenite is the most common mineral of molybdenum. 
The mineral is lead-gray with a metallic sheen that 
characteristically occurs in thin, tabular, hexagonal plates. 
and is disseminated in fine specks. The plates have an emi- 
nent basal cleavage, and are soft and flexible but not elastic. 
Molybdenite is commonly mistaken for graphite because of 
its similarity in structure and softness. It frequently occurs 
in pneumatolytie contact deposits associated with cassiterite, 
scheelite. wolframite, fluorite. etc. 

Wulfenite. a lead molybdate. is a heavy mineral with a 
resinous or adamantine luster. The mineral occurs in a well- 
formed crystal structure, commonly square tabular, but 
sometimes extremely thin. It displays a very smooth cleavage 
with red. orange, yellow, gray, and white colors. Wulfenite 
is of secondary origin, being found in lead and zinc deposits 
in the oxidation zone (11). 

Powellite, a calcium molybdate with calcium tungsten, 
is formed through the oxidation of molybdenite. The mineral 
is powdery and exhibits a tetragonal crystal structure with 
variable colors, including dirty white, straw yellow, greenish 
yellow, pale green, blue, and brown. Powellite is isomorphous 
and often associated with scheelite. This association helps in 
the identification of powellite because it fluoresces a golden 
yelllow color under ultraviolet light (11). 



Ferrimolybdite, long known as "molybdite," is a hydrous 
ferric molybdate. The mineral is commonly impure and most 
often is intimately associated with limonite. The mineral is 
soft with a distinctive canary yellow color. It occurs commonly 
in small amounts as an oxidation product of molybdenite. 

Other molybdenum minerals include chillagite, ilseman- 
nite, koechlinite, lingrenite, achrematite, belonisite, eosite, 
and jordisite (12). 



RESOURCES 

A total of 88 primary and byproduct properties in MEC's 
were evaluated to determine potential reserve-resources, 
grade, mine capacity, and costs of production. The 23 primary 
properties consisted of 9 producing mines and 14 undeveloped 
deposits. The 65 secondary properties (in which molybdenum 
is produced as a byproduct of copper production) consisted 
of 34 producing and 31 undeveloped deposits. Deposit loca- 
tions are shown in figure 2. Discussion of the geology of in- 
dividual primary deposits is included in the appendix. 

MEC primary molybdenum properties have approximate- 
ly 5,018 million mt of in situ ore, containing 9.6 billion lb of 
recoverable molybdenum and are all located in North America 
(table 8). Nearly 84 pet of the recoverable molybdenum would 
be from U.S. deposits, with Canada and Mexico accounting 
for 13 pet and 3 pet, respectively. 





20 



Btaftw 

23 <•.<■:-. 

24 Copp.' *» 
23 !#• -o -.- 
2* W»>t» 

27 ««!.>» 



2 -,<« •}«'-, »**>—. ■ 



IS. »■ Mi l M»^~? v 



30 •».»» CkMd 
I ' w ■ 



It -.w .... 

» :• .•< C4*i 



33 l'i«^ lo*ro* 

34 *>.-4..»«* 
V! - -c. 

M lit l-—y. 



KEr 



37 B a C Sptirig 
38. Tonopo* 

39 OvMtd 

40 T««>Bvti., 

41 UiMf.i o»« 
42- CfP'ol 6>3dod 

43 Owe*. %■».« 

44 P...0 van., 
43. He, 

47 Copp*. "07 

48 CM 

'< 3«« Uonu.1 
90 V«to4 Hill. 
31 3.1... 8.11 



• I 



33 »-. -. 

v. Ha 



M - In Km 



33 Cypru. Pimo 

36 Lo Condod 

37 C**mobODi 

38 O00O.P. 

39 C.r.o Colorado 
60 Uiehiquilloy 
«l El Aggilo 

82 *«ti.M 

83 To..off«otho 

84 CuoiOft. 
86 3o.to t*,%ri 
84 .■ • m 
67 Toqvopolo 

8ft C."o Colofooo 
89 Ow«oroda Bionco 

70 Ct.ogulco.not. 

71 [ki»Mi 

72 El lolvMor 



73. 80)0 Lo Alumpr.i 

74. Andocollo 

73 Lo. P.lomb... 

76 El Pochon 

77 Po.orMllo Sur 

78 Lo. Bronc. 

79 Andlna 

80 El T.ni.nt. 

61 So. Ch..m.rt 

62 Soiftdok 

63 Block Mountain 

64 Sipolar 
83 So.oi 
88 OK T.dl 
67 Yond..ra 
88 >.-.-■. 



LEGENO 
8 Primary molybdenum 
• Byproduct molybdenum 



Figure 2. — Molybdenum deposit locations, market economy countries. 



Table 8.— Primary molybdenum deposits and in situ demonstrated resources, market economy countries, January 1983 



Country and 
deposit name 



Owner 



Status' 



Type 2 



Demonstrated 

resources, 

10" mt 



Grade 
pet Mo 



Recoverable 

Mo in cone, 

10 6 mt 



Estimated 

ore capacity 

10 3 mt/yr 



Canada: 
Adanac 



Ajax Deposit . . 
Boss Mountain 

Endako 

Glacier Gulch . 

Kitsault 

Mt. Thomlinson 

Red Bird 

Trout Lake 



Subtotal 

Mexico: 

Cumobabi 

Opodepe 

Subtotal 

United States: 

Big Ben Deposit . 
Buckingham 

Deposit 

B&C Spring 

Climax Mines . . . 
Hall (Tonopah) 

Mine 

Henderson Mines 
Mt. Emmons 

Mt. Tolman 

Quartz Hill 

Questa Mines . . . 
Thompson Creek 
White Cloud 



Subtotal 
Total . . . 



Adanac Mining & 

Explorations Co 

Newmont Mining Corp 

Noranda Mines Ltd 

Placer Development Co 

AMAX Inc 

. . Do 

Kidd Creek Mines Ltd 

Phelps Dodge Corp. of Canada 
Newmont, 55 pet; ESSO, 45 pet 



Minera Cumobabi S.A. de C.V. . 
Compania Minera Fresnillo, S.A. 



AMAX Inc. 



Rocky Mt. Energy 
Sharon Steel 
AMAX Inc 



Anaconda Co 

AMAX Inc 

..do 

Colville Confederated Tribe . . . 
Pacific Coast Molybdenum Co. 

Molycorp 

Cyprus Mine Corp. 

ASARCO 



201 

179 
4 

187 
18 

104 
41 
81 
49 



5,018 



0.059 
.073 
.141 
.095 
.210 
.112 
.072 
.071 
.115 



.109 



229 

205 

9 

305 

57 
232 

44 
102 

85 



9,628 



4,760 
8,750 
857 
10,320 
1,050 
3,810 
2,493 
3,500 
2,600 





864 


.084 


1,268 


38,140 


s 


17 


.250 


67 


7,000 


s 


162 


.100 


241 


7,000 




179 


.114 


308 


14,000 


s 


107 


.096 


187 


5,350 


s 


217 


.057 


224 


7,000 


s 


34 


.080 


47 


2,198 


c 


375 


.210 


1,397 


17,123 


s 


143 


.096 


303 


7,000 


u 


223 


.251 


999 


9,710 


u 


115 


.323 


678 


6,602 


s 


900 


.060 


953 


19,050 


s 


1,362 


.082 


2,112 


19,591 


u 


95 


.186 


395 


5,877 


s 


175 


.112 


389 


8,051 


s 


229 


.081 


368 


7,938 




3,975 


.109 


8,052 


115,510 



167,650 



Producer; D Developing; E Explored. 
Surface; U Underground; C Combined. 



The resource from byproduct properties as estimated at 
30,535 million mt of ore, with recoverable molybdenum 
estimated at 6.8 billion lb (table 9). 



Primary Molybdenum Resources 

The United States has an estimated 8.0 billion lb of 
recoverable molybdenum from 12 primary mines. Five of 
these mines -Climax, Henderson, Thompson Creek, Hall, and 
Questa -were evaluated as producers, and one mine, Quartz 
Hill, was evaluated as developing property. The remaining 
six deposits have been explored but have no immediate plans 



for development. The present capacity from producing 
primary domestic deposits was estimated at 153 million lb/yr 
Mo; an additional capacity of 40 million lb/yr will be added 
when Quartz Hill starts production. 

Canada accounts for 1.3 billion lb of recoverable 
molybdenum from nine primary deposits. Current produc- 
tion comes from three mines with an installed capacity 
estimated at 23 million lb/yr. 

Mexico has two primary molybdenum deposits (a pro- 
ducer and a nonproducer), with total recoverable molybdenum 
estimated at 308 million lb. Molybdenum production from 
Cumobabi, the producing mine, is estimated at 2.7 million 
lb/yr, though a capacity expansion is being planned. 



Table 9.— Byproduct molybdenum deposits and in situ demonstrated resources, market economy countries, January 1983 

Country 



Argentina 

Canada 

Chile 

Fiji 

Iran 

Mexico 

Pakistan 

Panama 

Papua New Guinea 

Peru 

Philippines 

United States .... 

Total 



Demonstrated 


Av feed grade, 


pet 


Recoverable 


Estimated ore 


capacity, 10 3 mt/yr 


resources, 


Cu 


Mo 


Mo in cone, 


Producer 


Nonproducers 


10 6 mt 






10 6 lb 






1,279 


0.73 


0.014 


244 





37,569 


3,250 


.40 


.033 


873 


73,918 


61,836 


11,050 


1.32 


.060 


2,935 


74,443 


60,116 


813 


.49 


.014 


73 





14,200 


414 


1.13 


.030 


117 


13,200 





1,200 


.67 


.020 


317 


25,200 





348 


.43 


.006 


14 





3,500 


1,380 


.73 


.009 


172 





27,000 


791 


.81 


.015 


136 





34,312 


2,841 


.87 


.021 


705 


33,840 


14,805 


879 


.50 


.002 


25 


22,600 





6,290 


.62 


.019 


1,153 


268,538 


35,331 



30,535 



.89 



.034 



6,764 



511,739 



288,669 



Byproduct Molybdenum Resources 

The 21 U.S. copper properties analyzed for this report 
have the capability to produce a total of 1.2 billion lb Mo from 
demonstrated resources. Of these deposits. 14 were evaluated 
as producers, though many are presently temporarily shut 
down. These 14 producing mines have the capacity to pro- 
duce an estimated 47 million lb/yr Mo. 

Canada has recoverable molybdenum estimated at 873 
million lb from 13 copper deposits. At present, copper pro- 
ducers contribute about 21 million lb/yr Mo from 6 mines. 

The La Caridad copper mine in Mexico has a recoverable 
molybdenum resource estimated at 317 million lb. Current 
capacity is estimated at 10.1 million lb/yr. 

All molybdenum production in Chile is a byproduct of cop- 
per operations, with Chuquicamata and El Teniente account- 
ing for more than S2 pet of the total. Chile has an estimated 
2.9 billion lb Mo recoverable from 10 copper properties. 5 
of which are producing. At present, the five producing mines 
have a total installed capacity estimated at 45 million lb/yr 
Mo. Actual capacity may vary depending on the grade and 
recovery at the time. For example, in 1982. one major mine 
not only improved the mill recovery but also encountered a 
high-grade molybdenum ore body, causing a large increase 
in molybdenum output in that particular year. 

Molybenum resources in Peru come from eight copper 
deposits. Current production comes from four copper opera- 
tions, with Cuajone and Toquepala accounting for more than 
98 pet of the total. Demonstrated resources for the eight prop- 
erties evaluated is estimated at 2.8 billion mt of ore and 705 
million lb Mo (recoverable). The installed capacity from the 
four producing mines is estimated at 9.0 million lb/yr. 



Iran has a single source of molybdenum, the Sar 
Cheshmeh copper mine. The mine has an estimated reserve 
of 414 million mt ore. containing approximately 117 million 
lb Mo (recoverable). The installed capacity of the mine is 
estimated at 4.0 million lb/yr. 

Production of molybdenum in the Philippines comes from 
three small copper operations: Sipalay. Basay, and Black 
Mountain Mines. The total demonstrated resource from these 
mines is estimated at 879 millions mt containing a total of 
25 million lb Mo (recoverable). The present installed capaci- 
ty is approximately 1.0 million lb/yr. 

Among countries with nonproducing deposits. Argentina 
accounts for the largest molybdenum in situ resources with 
1.279 million mt ore from Bajo la Alumbrera, Paramillo Sur, 
and El Pachon deposits. The recoverable resource from these 
deposits is estimated at 244 million lb Mo, all of which would 
be recovered as a byproduct of copper operations. Fiji has 
one copper deposit, the Namosi. with in situ reserves 
estimated at 813 million mt ore. An estimated 73 million lb 
Mo is potentially recoverable. Pakistan also has one proper- 
ty, the Saindak Copper deposit, which contains an estimated 
14.3 million lb Mo (recoverable). 

One copper deposit in Panama contains molybdenum, the 
Cerro Colorado. An estimated 172 million lb Mo is potential- 
ly recoverable. Development of this deposit has been delayed 
because of the slumping copper market. Papua New Guinea 
has two deposits, the OK Tedi and Yanderra, from which 
about 137 million lb Mo is potentially recoverable. OK Tedi 
started initial production for gold in 1984. However, produc- 
tion of copper and molvbdenum is not scheduled to start un- 
til 1987. 



MINING AND PROCESSING TECHNOLOGY 



MINING METHODS 

Ore deposits are mined by either underground or open 
pit methods. The selection of a mining method for a given 
deposit is more or less controlled by the grade, size, shape, 
and attitude of the ore body. Normally, the ideal choice is 
the one that gives safe working conditions and yields the 
greatest economic profit. Since primary molybdenum deposits 
occur as low-grade, high-tonnage porphyry deposits, low-cost 
underground block-caving and open-bit operations are the 
most commonly used methods to extract the ore economically. 

Currently, of the nine primarily molybdenum producers, 
two use underground block-caving methods (Henderson and 
Questa), five use open-pit methods (Endako, Kitsault, 
Cumobabi. Thompson Creek, and Hall), and two use combined 
methods (Climax and Boss Mountain). Of the byproduct 
operations, six are mined by underground block-caving 
methods and the rest by open pit. 



BENEFICIATION 

To separate the molybdenite from the gangue minerals, the 
ore is crushed and ground to a size where the mineral is 
liberated. The size requirement is controlled by the ore 
characteristics, economics, and available processing 
technology. Molybdenite is a relatively easily flotable mineral, 
so concentration always involves crushing and grinding to 
release the mineral, followed by floatation. Crushing of 
molybdenite ore. as practiced by primary molybdenum pro- 



ducers, consists of primary, secondary, and tertiary crushing 
systems. Semiautogenous crushing is practiced at the 
Henderson and Thompson mines where run-of-mine ore is 
crushed through the primary stage only to take advantage 
of the grinding effect of the rock size. 

After crushing, the ore is fed to ball mills which are in 
closed circuit with classifiers. Most of the flotation reagents 
are added at the grinding stage. Final grinding is monitored 
closely to avoid the production of fines. 

Molybdenite flotation practices are very similar for all 
operations. The only noticeable difference is in the equipment 
sizes, where newer plants employ much larger, more efficient 
equipment than old plants. 

In normal flotation practice, the pulp is pumped through 
banks of rougher cells, to produce a rougher concentrate. This 
is then reground in closed circuit with a classifier and routed 
to the cleaner section. Generally three to four cleaner stages 
are required before a final concentrate is produced. The grade 
of the final concentrate is about 54 pet Mo (90 pet MoS 2 ). 

In the Cu-Mo flotation process, the rougher cells are 
designed to handle bulk flotation at the highest overall 
recovery of copper and molybdenite minerals at the coarsest 
grind possible. A much stronger collector such as xanthate 
is used for bulk flotation in the rougher cells, and a more selec- 
tive reagent is used in the cleaner cells. A nonselective frother 
is also used in the rougher cells, methylisobutyl carbinol 
(MIBC) being the most popular. 

Copper-molybdenum separation varies from one plant to 
another, especially in the use of chemical reagents. However, 
the most commonly used technique to recover molybdenite 



10 



from copper is the sodium hydrosulfide-sodium sulfide proc- 
ess. In this process, sodium hydrosulfide or sodium sulfide 
is added to the copper-molybdenite concentrate in a flotation 
procedure to depress the copper and ion sulfide minerals and 
allow the molybdenite to float (13). Sometimes cooking or 
steaming is done ahead of the rougher flotation circuit to 
reduce sulfide consumption. Although the hydrosulfide proc- 
ess can treat all Cu-Mo concentrate separations, the 
economics of the process may vary. This is mainly because 
of varying concentrate composition, especially in terms of 
mineral contaminants. The presence of contaminants such 
as talc, coal, and sulfur alter the entire process. 



OTHER PROCESSING 

Molybdenite concentrate (90 to 95 pet MoS 2 ) is processed 
in roasters to produce technical-grade Mo0 3 . Roasting is nor- 
mally performed in four- zone multiple-hearth roasters, where 
molybdenite is converted to technical-grade Mo0 3 
exothermically. 

The first zone is for preheating, final drying, and burning 
of residual flotation oils. Temperature increases exothermical- 
ly in the second zone, where the molybdenite is converted 
to Mo0 2 with a minor amount transformed to M0O3. In the 



third zone, both the remaining sulfide and dioxide are con- 
verted to M0O3. In the fourth zone, with about 95 pet of the 
molybdenite already oxidized, an exothermic reaction can no 
longer be sustained. Hence, supplemental heat is supplied to 
complete the removal of sulfur to a content of less than 0.1 
pet. 

The product, technical-grade Mo0 3 , contains about 88 to 
98 pet Mo0 3 . About 0.1 pet of the plant feed is lost in the dust. 

Ferromolybdenum production begins by blending a 
charge consisting of Mo0 3 , ferrosilicon, and iron oxide to at- 
tain a homogenous mixture. A starter mix composed of 
magnesium, aluminum, potassium nitrate, and iron oxide is 
sprinkled over the charge and ignited; it readily ignites and 
starts the exothermic reaction. The reaction generates heat 
high enough to initiate the ignition of the actual charge. The 
resulting molten bath attains a temperature of 3,300° to 
3,500° F in the final stage of the reaction. This is allowed 
to cool for at least 16 h. At this time, a metallic fer- 
romolybdenum button is formed, and subsequently quenched. 

The metallic button is allowed to cool for another 24 h, 
before the slag is separated from the ferromolybdenum metal. 
Following the smelting and cooling the ferromolybdenum 
metal is normally broken to minus 8-in size before it is crushed 
and screened to different sizes and specifications (11*). 



DEPOSIT EVALUATION PROCEDURE 



Illustrated in figure 3 is the flow of the Bureau's Minerals 
Availability program (MAP) evaluation process, from deposit 
identification to the development of availability curves. This 
flowsheet shows the various evaluation stages used in this 
study to assess the availability of molybdenum from individual 
properties. After a deposit was identified for analysis, an 
economic evaluation of the property was performed. Optimal 
mining and concentrating rates and other production 
parameters were chosen using current engineering principles. 
Startup dates for developing deposits were based on an- 
nounced company plans. For explored deposits, a near-term 
development schedule (5 to 10 yr) was developed. Planned 
expansions for operating mines were included when known. 

Information on average grades, ore tonnages, and dif- 
ferent physical characteristics affecting production was ob- 
tained from various sources, including Bureau of Mines and 
U.S. Geological Survey publications, professional journals, 
State and industry publications, company annual reports, 10K 
reports and prospectuses filed with the Securities and Ex- 
change Commission, private companies, and estimates made 
by Bureau personnel. Much of the foreign data was collected 
through a Bureau contract with Pincock, Allen and Holt Inc., 
of Tucson, AZ. 

Selection of deposits was limited to known deposits that 
have significant demonstrated reserves or resources. 
Reserves are material that can be mined, processed, and 
marketed at a profit under prevailing economic and 
technological conditions. Resources are concentrations of 
naturally occurring solid, liquid, or gaseous materials in the 
earth's crust in such form that economic extraction of a com- 
modity is currently or potentially feasible (15). 

For the deposits analyzed, tonnage estimates were made 
at the demonstrated resource level based on the mineral 
resource-reserve classification system developed jointly by 
the Bureau of Mines and the U.S. Geological Survey (15). The 
demonstrated resource category includes measured plus in- 



dicated tonnages (fig. 4). Generally, reserve and resource ton- 
nage and grade calculations presented in this report were 
computed from specific measurements, samples, or produc- 
tion data, and from estimations made on geologic evidence. 
The deposits included in the analysis had to meet the 
following criteria: 

1. Producing properties accounting for at least 85 pet 
of the molybdenum production from each significant produc- 
ing country. 

2. Developing and explored deposits where the 
demonstrated molybdenum reserve-resource quantity was 
equivalent to at least the lower limits of the reserve-resource 
quantity of the producing deposits. 

3. Past-producing deposits where the remaining 
demonstrated molybdenum reserve-resource quantity was 
equivalent to at least the lower limits of the reserve-resource 
quantity of the producing deposits. 



ASSUMPTIONS 

The objective of the engineering-economic analysis for 
each deposit was to determine the total cost necessary to pro- 
duce a specified level of output from the deposit. Total cost, 
also called commodity or incentive price, is defined as the 
average total cost of production for the deposit. In this study, 
profit computed at a 15-pct discounted-cash-flow rate of 
return (DCFROR) was included in the total cost. Total cost, 
then, is the minimum molybdenum price (in constant dollars) 
at which a firm would be willing to develop its property; at 
this price, the firm would recover its investment and make 
a 15-pct profit. 

Determinations of the quantity of molybdenum that could 
be produced and the cost required to achieve this production 
were based on the following assumptions: 

1. Each operation will produce at full planned operating 



Identification 

and 

selection 

of deposits 



Tonnage 

and 

grade 

determination 



Engineering 

and 

cost 

evaluation 



Deposit 

report 

preparation 



Mineral 

Industries 

Location 

System 

(MILS) 

data 



MAP 

computer 

data 

base 



MAP 

permanent 

deposit 

files 



Taxes, 
royalties, 

cost 
indexes, 
prices, etc. 



Data 
selection 

and 
validation 



Economic 
analysis 



Data 



Availability 
curves 



Analytical 
reports 



u 



11 



Variable 

and 

parameter 

adjustments 



Sensitivity 
analysis 



Data 



Availability 
curves 



Analytical 
reports 



y 



Figure 3.— Minerals Availability program evaluation workflow. 



Cumulative 
production 



ECONOMIC 



MARGINALLY 
ECONOMIC 



SUBECONOMIC 



IDENTIFIED RESOURCES 


UNDISCOVERED RESOURCES 






Demonstrated 


Inferred 


Probability range 


Measured 


Indicated 


(C 

Hypothetical 


Speculative 












Res 


erve 


Inferred 






ba 


se 


reserve 
base 


1 








r 


1 









Other 
occurrences 



Includes nonconventional and low-grade materials 



Figure 4. — Mineral resource classification categories. 



12 



Table 10.— Byproduct commodity prices, market economy 
countries, January 1983 

Price, $/lb 

Tungsten $3.24 

Tin 5.53 

Copper .78 

Molybdenum 1 3.45 

'Produced as a byproduct of copper production. 

capacity throughout its life (capacities were based on 1983 
and/or 1984 company plans or engineering judgments). 

2. Competition and demand conditions are assumed such 
that each operation will be able to sell all its output at its 
total production cost. This condition implies that the level 
of molybdenum demand will support the highest cost deposit, 
or that existing Government subsidies will equal the dif- 
ference between the market price and the total cost for each 
submarginal deposit. 

3. All byproducts will be sold at the prices shown on table 
10. 

4. Production costs are for concentrates sold f.o.b. mine; 
i.e., no transportation or roasting costs are included. 

Time lags involved in filing environmental impact 
statements and receiving necessary permits, financing, etc., 
were not included in the analysis. Existing laws and regula- 
tions, environmental, political, legal, or other constraints may 
limit production from some of the deposits included in this 
study. 

The byproduct prices used in this study (table 10) were 
based on 1983 averages. Because the study was conducted 
using constant 1983 dollars, no escalation of either costs or 
prices was included. 

COST ESTIMATION 

When possible, actual company cost data were used. If 
these data were not available, the required capital and 
operating costs were estimated by standardized costing 
techniques. 

In some cases costs were estimated from a costing system 
prepared for the Bureau (16). This system is designed to 
prepare capital and operating cost estimates and is based on 
an average of the costs for existing mining operations in the 
United States and Canada. Correct use of this costing system 
will produce reliable estimates, which historically have fallen 
within 25 pet of actual costs. 



Individually deposit cost data were used to perform an 
economic analysis for each property. Capital and operating 
costs for developing and explored deposits were adjusted to 
average 1983 dollars. Mine and mill capital costs incurred 
prior to 1983 by producing mines (and some developing and 
explored deposits) were adjusted to average 1983 using the 
remaining book value of the investments. 

Capital expenditures were calculated for exploration, ac- 
quisition, development, and mine and mill plant and equip- 
ment. Capital expenditures for mining and processing 
facilities include the costs of mobile and stationary equipment, 
construction, engineering, infrastructure, and working 
capital. Infrastructure includes, among other things, the costs 
of the water system, power system, fire protection, roads, 
port facilities, construction of necessary rail facilities, and, 
in remote areas, construction of town and housing facilities. 
Working capital is a revolving cash fund for such operating 
expenses as labor, insurance, supplies, and taxes. 

Mine and mill operating costs were also calculated for 
each deposit. The total operating cost is a combination of 
direct and indirect costs. Direct operating costs include direct 
and maintenance labor, materials, payroll overhead, and 
utilities. Indirect operating costs include administrative costs, 
facilities maintenance and supplies, research, and technical 
and clerical labor. Other costs not included in operating costs 
but used in the analysis include deferred expenses, deprecia- 
tion, insurance, interest payments (if applicable), and taxes. 

The Bureau previously developed a Supply Analysis 
Model (SAM) to perform an economic analysis which presents 
the result as the primary commodity price (total production 
cost) needed to provide a stipulated rate of return (17). The 
DCFROR, used in this study, is most commonly defined as 
the rate of return that makes the present worth of cash flows 
from an investment equal to the present worth of all after- 
tax investments (18). For this study, a 15-pct DCFROR was 
considered necessary to cover the opportunity cost of capital 
plus risk. For some Government-owned operations, a 15-pct 
DCFROR may not be required for continued production. 
However, for comparison purposes, each deposit was ana- 
lyzed at this DCFROR. 

For producing mines, analysis was also performed at a 
0-pct DCFROR, which is roughly equivalent to a breakeven 
production cost. In the short run, a mine may continue to 
produce at molybdenum prices even below this cost in an- 
ticipation of improved market conditions. 






OPERATING COSTS 



The average total capital and operating costs calculated 
for each of the deposits analyzed include mining, concen- 
trating, and capital recovery, taxes, and profit. These costs 
often vary greatly, depending on such factors as size of opera- 
tion, mining method, deposit location, stripping ratio, depth 
of ore body, grade of molybdenum and byproducts, process- 
ing losses, energy and labor costs, and applicable tax 
structure. 

The operating costs presented in this section are based 
on mining ore and concentrating the ore over the life of the 
operation. Capital costs for deposits not producing at the time 
of the study reflect the total investment required to develop 
a mine, construct all facilities, and begin production. Capital 
costs for producing mines have less effect because some of 
the mines have been producing for many years and a large 
portion of the initial cost has been depreciated. 



Weighted average cost data for all primary mines 
evaluated in the United States and Canada are shown in table 
11 on a per-ton-of-ore basis and in table 12 on a per-pound- 
of-molybdenum basis. To maintain confidentiality, cost data 
on the two Mexican deposits are withheld. The U.S. produc- 
ing mines consist of two underground, two surface, and one 
combined (underground-surface) operation; the Canadian 
mines includes two surface mines and one combined 
operation. 

The average operating cost on a per-ton-of-ore basis for 
producing U.S. mines (table 11) is more than twice that of 
the Canadian mines. This is attributed to the high stripping 
ratio of U.S. surface mines (3:5:1.0) and the fact that about 
50 pet of the U.S. tonnage is from underground operations. 
In nonproducing mines, the projected cost of U.S. mining is 
less than half that of the Canadian operations. This is because 



13 



Table 11.— Estimated cost of mining and milling operations from 

primary producers in the United States and Canada, 

January 1983 







Prod 


ucers 


Nonprod 


ucers 




United 


Canada 


United 


Canada 






States 




States 




Number of 












deposits . 




5 


3 


7 


6 


Total annual 


ore 










capacity. . 


10'mt. . 


47.781 


14.987 


67.730 


23.153 


Av feed 












grade . .pet Mo. . 


0.1696 


0.092 


0.100 


0.073 


Av operating 


cost. 










S/mt ore: 












Mine . . 




7.03 


$2.79 


$2.87 


$6.78 


Mill . 




3.14 


$2.83 


S3.40 


$2.78 









six of the seven projected U.S. mines would use surface 
methods, whereas four of the six projected Canadian mines 
would be underground. Comparing U.S. mines, the producers 
show a much higher mining cost than the nonproducers. This 
is due to the higher stripping ratio experienced by producers 
and the higher percentage of ore produced by underground 
methods. 

The per-ton cost for beneficiation reflects small dif- 
ferences between U.S. and Canadian operations. The five pro- 
ducing U.S. mines averaged S3.14/mt ore. while the three 
Canadian mines averaged S2.83/mt. The added cost of 
byproduct recovery made the U.S. operations slightly higher 
than Canadian mines, which produce no byproducts. 

When costs are converted from dollars per metric ton 
of ore to cents per pound of molybdenum contained in con- 
centrate, the average operating cost for producing U.S. mines 
-2.16/lb for mining and S0.99/lb for milling. 
Operating costs for Canadian mines average $3.3S71b, $1.54/lb 
for mining and S1.84/lb for milling. On a cost per metric ton 
of ore basis, mine operating costs for producing U.S. mines 
are 2.5 times greater than for Canadian producing mines. 
However, owing to the much higher ore grade of the mines. 
costs on a per pound basis are only 1.4 times higher. For mill- 
ing. U.S. mines have a cost advantage over Canadian mines 
owing to a higher ore grade (0.1696 pet compare with 0.092 
pet) and economies of scale of the larger U.S. milling opera- 
tions. The annual capacity of the five U.S. milling operations 
in 1983 averaged 9.6 million mt ore. while the three Cana- 
dian mines averaged only 5.0 million mt. The difference in 
mill operating costs between U.S. producing and nonproduc- 
ing mines is due primarily to the much lower grade (0.09 pet 
compared with 0.1696 pet) of the nonproducing deposits. 

Taxes for producing mines in the United States and 
Canada are nearly equal, averaging SO.lO/lb in the United 
States and S0.11/lb in Canada. Taxes are greater for non- 
producers because, in most cases, the revenues required to 



Table 12.— Estimated mine and mill operating costs' for primary 

molybdenum procuers in the United States and Canada, 

January 1983 

(Dollars per pounds molybdenum contained in concentrate) 

Producers Nonproducers 

Cost United r^«-«j«> United „ . . 
States' Canada States' Canada 

Operating cost: 

Mine $2.16 $1.54 $1.43 $4.30 

Mill .99 1.84 2.52 2.27 

Total 3.15 3.38 3^91 (f57 

Taxes 10 .11 .17 .12 

Capital recovery 52 .60 .96 1.77 

Byproduct credit (-.30) (-.00) (-.25) (-.09) 

Breakeven cost' ... 3.47 4.09 4.83 8.37 

Total cost 3 4.28 5.62 9.03 27.26 

'Costs based on total annual capacity for molybdenum in concentrate 
as shown below: 

Number Mo in cone, 
of mines 10" Ib/yr 



Producers: 

United States 
Canada 

Nonproducers: 
United States 
Canada 



161 
25 

133 
33 



'Mine and mill cost, plus taxes and capital 
recovery, less byproduct credits (as shown). 
'Breakeven cost plus profit at a 15-pct DCFROR. 



cover the higher production costs (incl ding recovery of 
capital) are greater. 

The capital recovery cost reflects the complete recovery 
of all capital investments allocated on a per-pound-of- 
production basis over the life of the mine. This cost averaged 
$0.52/lb for U.S. producers and $0.60/lb for Canadian. Costs 
for nonproducing deposits are much higher (particularly in 
Canada), since none of the capital cost has been depreciated, 
as it has for producing mines. 

Byproduct credits (W0 3 , Sn, and Cu) provide an added 
benefit to U.S. producers, averaging $0.30/lb Mo. Canadian 
producing mines, on the other hand, produce no byproducts. 

Producing U.S. mines average $3.47/lb, while Canadian 
producers average $0.62/lb higher at $4.09/lb. Total costs of 
nonproducing U.S. deposits are more than double those of 
producing mines; in Canada the nonproducer total cost is 
nearly triple the producer total cost. 

Breakeven cost reflects the cost of production at which 
the mines would break even and cover all production costs 
after credit for byproducts. Total cost includes net cost plus 
profit at 15-pct DCFROR. Total costs are much higher for 
nonproducers because greater revenues are required to pro- 
vide profit on the larger capital investment. 



CAPITAL COSTS 



To estimate the capital costs for explored and develop- 
ing properties, exploration, acquistion, development, mine 
and mill plant and equipment, and infrastructure costs were 
calculated. Capital costs beyond beneficiation, such as for 
roasting, were not included in the analyses. A total of 14 prop- 
erties, 9 surface and 5 underground, were evaluated for this 
section. Capital costs according to mine type and ore capaci- 
ty are shown in table 13. All costs were adjusted to January 
1983 dollars. Actual cost for individual deposits may vary 
greatly depending on required infrastructure, exploration and 



development works, size of operation, characteristic of the 
orebody, and complexity of the ore. 

The average capital cost of nine surface mining opera- 
tions was estimated at $269 million, or $18.92 per pound of 
annual molybdenum capacity. This compares with an average 
cost of five underground operations of $286 million, 
representing $19.60 per pound of annual capacity. 

In both surface and underground operations, cost per 
pound of annual capacity was lower for the larger mines, 
representing some economies of scale. However, most of the 



14 



Table 13.— Estimated capital costs for developing and explored molybdenum deposits, market economy countries, January 1983 

(Thousand dollars) 



Number 

of 
mines 



Av 
capacity, 
mt/d ore 



Acquisition, 
exploration, 
development 



Mine 



Mill 



Infra- 
structure 



Total 
cost 



Capital cost, 

per lb 

annual capacity 



Surface: 

< 10,000 2 

10,001 to 20,000 4 

>20,000 3 

Total or average . . . 

Underground: 

< 10,000 

> 10,000 

Total or average 5 



8,141 


$23,000 


$30,830 


$41,400 


$44,030 


$139,260 


$35.80 


17,221 


17,320 


33,300 


97,560 


25,990 


174,170 


17.57 


43,840 


54,150 


103,670 


292,960 


42,250 


493,030 


16.31 



9 


23,067 


$31,490 


$55,933 


$143,973 


$37,423 


$268,819 


$18.92 


3 
2 


5,066 
25,200 


$19,230 
195,100 


$19,850 
60,170 


$38,950 
103,610 


$38,150 
97,790 


$116,180 
456,670 


$26.39 
18.23 



15,133 



$107,165 



$40,010 



$71,280 



$67,970 



$286,425 



$19.60 



capital cost differential was due to higher proportional costs 
for exploration and development and infrastructure in the 
smaller mines; for example, infrastructure costs for the 



smallest group (less than 10,000 mt/d ore) of surface opera- 
tions were actually higher than total such costs for the largest 
(greater than 20,000 mt/d ore) surface mines. 



MOLYBDENUM AVAILABILITY 



EVALUATION METHODOLOGY 

After cost and resource data were determined for each 
deposit, total and annual resource availability curves were 
constructed to illustrate molybdenum availability. These 
curves are discontinuous functions relating the total cost (as 
defined in the "Assumptions" section) for a deposit to its level 
of production. The total or annual quantity of molybdenum 
from each deposit was accumulated from lowest to highest 
total cost to show molybdenum availability. 

A total resource availability curve is not an ordinary sup- 
ply curve because it does not consider the time parameter 
and is not the industry's marginal cost curved. Rather, a total 
resource availability curve is an aggregate of the total pro- 
duction potential at a stipulated cost that covers full produc- 
tion costs. 

For the engineering analysis, it was necessary to deter- 
mine a development schedule for each property. For produc- 
ing mines, expansions considered to have a high probability 
of occurring were included. For nonproducing deposits, the 
time required for development depends upon the exploration, 
extent of preproduction development, plant construction, and 
infrastructure requirements. Annual resource availability 
curves are disaggregations of total resource curves to an an- 
nual production basis. Compared with total availability 
curves, annual availability curves more closely resemble true 
supply curves since they show annual production; but they 
also indicate average total cost of production rather than 
marginal cost. 

Separate annual availability curves were constructed for 
producing mines and nonproducing (developing and explored) 
deposits. Annual curves for producing mines show the 
molybdenum capacity of existing mines and planned expan- 
sions when known. Annual curves for most nonproducing 
deposits are not related to any given year, since the startup 
year is uncertain. They do, however, show required lead times 
before production can begin and indicate potential annual pro- 
duction capabilities. 



TOTAL AVAILABILITY 

At the demonstrated resource level potential recoverable 
molybdenum from primary mines was estimated at 9.6 billion 



lb, with an additional 6.6 billion lb available from primary 
copper mines. 

With 15-pct DCFROR on invested capital, a total of 8.9 
billion lb would be available from the primary deposits at pro- 
duction costs ranging from $3.20/lb to $14/lb Mo (figure 5 
and table 14). The remaining 712,000 lb would have a pro- 
duction cost exceeding $14/lb. In January 1983, dealers were 
selling the metal for $2.47/lb, a price well below the produc- 
tion cost of primary producers. Analyses indicated that vir- 
tually the only supply source that could provide molybdenum 
at this price would be byproduct producers, especially from 
the foreign copper operations. 

At a price of $10/lb, approximately equivalent to the 1980 
selling price, the available resource would be 7.9 billion lb. 
However, at $4.50/lb, the 1982 selling price, the available 
resource drops to 2.5 billion lb. When dealers were selling 
the metal at $2.47/lb, analyses indicated that only one primary 
mine could cover production costs (DCFROR, breakeven cost) 
(fig. 6). Costs reflected in figure 6 include capital recovery; 
hence these costs should not be interpreted as cash cost 
equivalents. 

Producing mines account for 43 pet of the tonnage poten- 
tially recoverable from primary properties, while deposits 
under development account for 22 pet; explored deposits, hav- 
ing no specific plans for development, account for the remain- 
ing 35 pet. 

The weighted-average cost of production for producing 
mines (including a 15-pct DCFROR) is estimated to be 
$4.46/lb Mo; nearly 2.5 billion lb is available at a molybdenum 
price of $4/lb. At $6/lb, the available molybdenum from pro- 
Table 14.— Molybdenum potentially available from primary pro- 
ducing, developing, and explored deposits in market economy 
countries at selected 1983 prices, at a 15-pct DCFROR 
(Million pounds of contained molybdenum) 

T .... Producing Developing and 

lotai cost vip mines explored deposits Total' 

Under $4.00 2,463 2,463 

$ 4.01 to $ 6.00 1,002 1,002 

$ 6.01 to $ 8.00 630 610 1,240 

$ 8.01 to $10.00 3,200 3,200 

$10.01 to $14.00 1,009 1,009 

Above $14.00 712 712 

Total 1 4,096 5,531 9,626 

'Totals may not add owing to independent rounding. 



15 



-69- 

ro 

CD 

c 
o 

"3 



o 
o 



< 
h- 

o 




12 3 4 5 6 7 8 

TOTAL RECOVERABLE MOLYBDENUM, I0 9 lb 
Figure 5. —Total molybdenum available from primary deposits, market economy countries. 



10 



6.00 



00 
CD 



c 
o 



CO 

o 
o 



O 




1.0 1.5 2.0 2.5 3.0 

TOTAL RECOVERABLE MOLYBDENUM, I0 9 lb 
Figure 6. —Total molybdenum available from producing minesat a 0-pct DCFROR, market economy countries. 



4.5 



16 



during mines increases by 1.0 billion lb. At these prices no 
tonnage is available from the nonproducers. However, at 
$8/lb, an additional 1.2 billion lb would be available, nearly 
half of which would be from deposits not currently produc- 
ing. At prices exceeding $8/lb, an additional resource of 4.9 
billion lb is potentially available, entirely from nonproduc- 
ing deposits. 

The total potential availability of primary molybdenum 
from properties within Canada and the United States con- 
stitutes 97 pet of the total resource. Shown in figure 7 are 
curves illustrating the molybdenum availability of each coun- 
try. These data are grouped in various price categories in 
table 15. At a price under $4/lb and a 15-pct DCFROR, the 
United States has a potential available resource of 2.4 billion 



Table 15.— Molybdenum potentially available' within the United 
States and Canada, at a 15-pct DCFROR 

(Million pounds or recovered molybdenum) 

Tota 'cost, United Canada T , 
$/lb States 

Under $4.00 2,396 2,396 

$ 4.01 to $ 6.00 697 305 1,002 

$ 6.01 to $ 8.00 757 241 998 

$ 8.01 to $10.00 3,200 3,200 

$10.01 to $14.00 952 57 1,009 

Above $14.00 48 664 712 

Total' 8,050 1,267 9,317 

'Includes both producers and nonproducers. 



lb, enough to supply current domestic requirements for at 
least 40 yr. A price of $6/lb would bring an additional resource 
of 697 million lb from U.S. deposits for a total of 3.1 billion 
lb. At the same price, Canada could produce a total of 305 
million lb. At a price exceeding $8/lb, U.S. deposits could pro- 
duce an additional 4.2 million lb, while Canada could mine 
an additional 721 million lb. 



ANNUAL AVAILABILITY 

The estimated molybdenum production capacities for the 
deposits analyzed are shown in table 16. At full capacity 
levels, a total production of 337 million lb is available from 
the market economy countries- 179 million lb from the pro- 
ducing mines and 158 million lb from nonproducers. All pro- 
duction capacity from operating mines would be available at 
a cost of $8/lb or less, while explored deposits could only con- 
tribute 25 million lb at that price. Additional production 
capacities would be available at costs ranging up to $14/lb, 
all from developing and explored deposits. 

Figure 8 shows potential annual molybdenum production 
at various cost ranges for producing mines and nonproduc- 
ing deposits. The large increase in production from 1983 to 
1984 for producing mines occurs because many mines were 
shut down in 1983 and were assumed to be reopened in 1984. 
The production from 1984 to 2000 for these mines represents 
molybdenum output potential at full-capacity levels of pro- 



30 



CO 
O 
o 

_l 

I 



25- 



20- 



15- 



10- 



5- 



-Canada 



/ 



/ 



/ 



■United States 



-L 



-L 



J_ 



RECOVERABLE MOLYBDENUM, I0 9 lb 
Figure 7. —Total molybdenum potentially available in the United States and Canada from producing mines and 
nonproducing deposits. 



17 



350 




1989 



1991 



1993 



1995 



1997 



1999 



2001 



Figure 8.— Potential annual production of molybdenum from producing mines and nonproducing deposits at various cost ranges, 

market economy countries. 



Table 16. — Potential 1983 molybdenum production capacities 

from primary molybdenum mines and deposits in market 

economy countries, at a 15-pct DCFROR 

(Million pounds of contained molybdenum) 

Total cost S/lb Producng Developing and ~~ 

mines explored deposits Total 1 

Under $3.50 44 44 

S 3.51 to S 4.75 74 74 

S 4.76 to S 6.00 34 34 

S 6.01 to $ 8.00 27 25 52 

S 8.01 to S 9.00 62 62 

S 9.01 to S12 00 40 40 

S12.01 to S14.00 

Above $14.00 31 31 

Total 179 158 337 

Installed capacities for producing mines and projected capacities for 
developing and explored deposits. 



duction. The fact that the curves for producing mines do not 
decrease indicates that these mines have sufficient reserves 
to produce at full capacity until sometime after the year 2000. 
At a cost of S3.50/lb with 15-pct DCFROR, an annual pro- 
duction of 44 million lb would be economically available from 
producing mines. At S4.75/lb, production would increase to 
a total of 118 million lb/yr; while at S8, all producing mines 
could economically operate. 

Because startup dates for developing and explored 
deposits were not known, construction of annual availabili- 
ty curves for them were based on the assumption that 
preproduction would begin in year "N" (fig. 9). These curves 
indicate that several years would be required from the year 
development begins before any production could occur. 



Although an additional 133 million lb/yr Mo could be produced 
from these deposits, a price exceeding $8/lb would be re- 
quired. Therefore, for most of these deposits, production in 
the near future appears unlikely. 



BYPRODUCT MOLYBDENUM TOTAL 
AVAILABILITY 

A significant portion of molybdenum production is as a 
byproduct of copper; production from this source has been 
increasing in recent years. A total of 65 copper deposits were 
analyzed for molybdenum production, 34 producers and 31 
nonproducers. A total of 14 domestic copper operations were 
evaluated as producers, some of which are temporarily closed. 

As shown in figure 10, the total byproduct availability 
from all minas evaluated amounts to approximately 6.6 billion 
lb Mo at a price up to $3.80/lb Cu, with producers account- 
ing for over 65 pet of the total. As shown in table 17, a total 
of 1,435 million lb Mo could be economically mined at a cop- 
per price under $0.50/lb, with an additional 1,986 million lb 
available at prices up to $0.75/lb. At higher copper prices (ex- 
ceeding $2.25/lb) a total of 6,608 million lb Mo is potentially 
available, two-thirds of which would be from producing mines. 

Annual availability from all mines evaluated amounts to 
an annual capacity of 47.1 million lb Mo. Table 18 shows the 
U.S. molybdenum capacity from operating or temporarily 
shut down copper mines for 1983. At a copper price of 
$0.75/Ib the domestic molybdenum producers can supply 22.3 
million lb Mo from two copper mines. An additional capacity 
of 6. 1 million lb can be generated at a copper price of $1 ,00/lb. 
The remaining capacity requires a copper price gre »ter than 



18 



80 



70 



io E 60 
O 



^ 50 

UJ 

Q 

Q 40 



30 



UJ 

_l 
CD 
< 

a: 

UJ 

ui 
or 



10 



N Year preproduction 
development begins 




N+2 



N+4 



N+6 



N+12 



N+14 



N + 16 



N+18 



Figure 
market 



N+8 N+IO 

YEAR 
9.— Potential annual production of molybdenum from developing and explored deposits at various cost ranges, 
economy countries. 



o 



ro 
oo 
o> 



o 

~3 



g |.50 







2 3 4 5 6 

TOTAL RECOVERABLE MOLYBDENUM, I0 9 lb 
Figure 10.— Total available molybdenum byproducts from copper deposits, market economy countries. 



19 



$1.00/lb to be economically extractable. At copper prices 
above Sl.OO/lb molybdenum production is questionable since 
many of these mines are now shut down. It is likely that many 
of these mines will remain closed owing to the availability 
of cheaper byproduct molybdenum from copper operations 
in foreign countries. 



Table 17.— Total molydenum byproduct potentially available in 

market economy countries at selected copper production costs, 

at a 15-pct DCFROR 

(Million pounds of molybdenum) 

^ •«. Producing Developing and 

Copper price. S/lb 3 , ; ." ,. _ , 

mines explored deposits Total 

Under $0.50 1.005 430 1.435 

S0.51 to S0.75 1.810 176 1.986 

S0.76toS1.00 760 136 896 

S1.01 to S1.50 706 443 1,149 

S1.51 to S2.25 137 715 852 

Above S2.25 290 290 

Total 4.418 2.190 6,608 

Table 18.— Annual U.S. byproduct molybdenum capacity and 

total demonstrated resources of recoverable molydenum from 

evaluated U.S. copper operations at selected copper prices, at 

a 15-pct DCFROR 

(Million pounds of molybdenum) 

_ __. Annual Total 

Copper price. S/lb capacity. 1983 resources 

Under S0.75 22.3 294.4 

$0.76 to S1.00 6.1 131.7 

$1.01 to $1.50 16.2 495.9 

Above $1.50 2^5 7.6 

Total 47.1 929.6 



Estimated annual production capacities for byproduct 
molybdenum from primary copper deposits are shown in table 
19. Capacities, as shown, were estimated at full designed 
capacity for the years 1983 and 1991. A total production 
capacity of 109 million lb was estimated for 1983 from pro- 
ducing mines, with the United States contributing 47 million 
lb. As shown, there are planned capacity increases in pro- 
ducing mines of over 25 pet by 1991. In addition, deposits 
not now producing have the potential to add nearly 70 million 
lb/Mo, although for most deposits, much higher copper prices 
would be required. 

Since copper price influences molybdenum production, 
potential annual molybdenum capacity was analyzed on the 
basis of copper price (fig. 11). As shown, at a copper price 
of $0.50/lb, annual production capacity in 1983 was estimated 
at 25 million lb from seven properties. As these mines ex- 
pand molybdenum production capabilities, capacity could ap- 
proach 50 million lb/yr. At a copper price of $l/lb, produc- 
tion capacity for 1983 increases to 64.0 million lb. At the same 

Table 19.— Molybdenum byproduct potential annual production 

for 1983 and 1991 from market economy countries, at a 15-pct 

DCFROR 

(Million pounds of contained molybdenum) 





1983 capacity: 
Producing 




1991 capacity 




Copper price 


Producin 


g Nonproducing 




$/lb 


mines 


mines 


deposits 


Total 


Under $0.75 


51.7 


74.2 


20.4 


94.6 


$0.75 to $1.00 . . . 


12.4 


26.0 


0.0 


26.0 


$1.00 to $1.50 . . . 


34.6 


30.4 


21.6 


52.0 


$1.50 to $2.25 . . . 


10.5 


8.7 


27.6 


36.3 


Total 


109.2 


139.3 


69.6 


208.9 



225 



zz: - 



to 
o 



UJ 
Q 

CD 

o 



I75 - 



I50- 



I25 - 



UJ ICO 



CD 

< 
or 

UJ 
UJ 

or 




200I 



Figure 11. — Potential annual capacity of molybdenum byproducts at selected copper prices, market economy 
countries. 



20 



price, 124.8 million lb/yr capacity would be available from 
28 properties in 1991, 80 pet of which would be from mines 
currently producing. As shown, molybdenum as a byproduct 
of copper production could exceed 200 million lb/yr. However, 
prices well above $1.00/lb would be required. 

Table 20 shows the 1983 estimated installed molybdenum 
capacity on a country basis for producing mines. Among 
primary producers, the United States accounts for 153 million 
lb/yr or 85 pet of the total capacity, while Canada and Mex- 
ico hold 13 pet and 2 pet, respectively. In byproduct produc- 
tion, the United States has the capacity to produce 47 million 
lb/yr, 34 pet of the total. Chile has a production capacity of 
45 million lb/yr, with Canada following at 21 million lb/yr. 
The remaining capacity is divided between four countries: 
Mexico, Peru, Iran, and the Philippines. 

As shown in the table, the installed capacity far exceeds 
the MEC production, which has averaged 178 million lb/yr 
over the last 10 yr. In addition, private inventories estimated 
at 200 million lb in 1983 have contributed to the oversupply 



Table 20.— Estimated total 1983 molybdenum capacity from 
primary and byproduct producers in market economy countries 

(Million pounds of molybdenum) 

Country Primary Byproduct Total 

United States 153 47 200 

Canada 23 21 44 

Mexico 3 10 13 

Chile 45 45 

Peru 9 9 

Iran 4 4 

Philippines 1 1 

Total 179 137 316 



of molybdenum (19). As a result, there is little likelihood for 
explored primary deposits to be developed in the foreseeable 
future. It is more likely that planned expansions by byproduct 
producers will continue to affect primary production and, as 
a result of continued overcapacity conditions, molybdenum 
price will tend to remain low. 



CONCLUSIONS 



The United States has about 8.1 billion lb Mo 
(recoverable) from primary deposits and 1.2 billion lb as a 
byproduct of copper production. This constitutes 84 pet of 
all recoverable primary resources located in the MEC'S, and 
17 pet of the recoverable byproduct resource. The current 
U.S. production capacity is estimated at 153 million lb from 
primary producers and 47 million lb from byproduct pro- 
ducers, a total of 200 million lb/yr. This capacity is well above 
the domestic consumption requirement, which has a 10-yr 
average of about 57 million lb/yr. Disregarding economics, 
available U.S. resources could supply current domestic de- 
mand at this level for at least 160 yr. Assuming production 
at the average rate over the last 10 yr (about 114 million 
lb/yr), U.S. resources could last for over 80 yr. 

Applying profitability at a 15-pct DCFROR on invested 
capital and a price of $4/lb Mo, 2.5 billion lb of Mo could be 
recovered from MEC primary mines. If the molybdenum 
price were to increase to $6/lb, an additional 1 billion lb would 
be available. There are also large resources (5.5 billion lb Mo) 
potentially available from primary deposits that are not now 
producing; however, prices exceeding $14/lb would be 
required. 

With such a large resource base located within the ter- 
ritorial boundaries of the United States, molybdenum 



availability is well assured regardless of international trade 
disruption. However, most of these resources can only be pro- 
duced at prices higher than those prevailing today (1983). 

As major international molybdenum suppliers, primary 
U.S. producers are threatened by foreign byproduct pro- 
ducers. As new foreign byproduct production capacity comes 
on-stream, large quantities of molybdenum will be available 
to the international market. In effect this could dislocate some 
primary suppliers, which require higher molybdenum prices 
in order to profitably operate. In recent years, primary mines 
have cut back production, and in 1983 production at all 
primary U.S. mines was halted. Unless market conditions 
significantly improve, the outlook for these primary pro- 
ducers is bleak. 

Byproduct production is less sensitive to molybdenum 
price changes since the operation is more dependent on cop- 
per price. In addition, many of the byproduct properties are 
located in countries where employment and the need for 
foreign currency are the primary concerns rather than pro- 
fitability. Even under continued poor economic conditions, 
molybdenum production from these sources will continue to 
be available. Furthermore, the production from these coun- 
tries is expected to increase, owing to planned copper mine 
expansions and new mine developments. 



21 



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22 



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23 



APPENDIX.— DEPOSIT DESCRIPTIONS 
FOR PRIMARY MOLYBDENUM 



UNITED STATES 
Alaska 



Quartz Hill 



The Quartz Hill deposit is located on a knoll bounded by 
the Wilson Arm-Smeaton Bay Fjords on the north and the 
Boca de Quadra fjord on the south. It lies within a transi- 
tional zone between the Wrangell-Revillagigedo Belt 
metamorphic complex to the west and the massive Coast 
Range Batholith rocks to the east. The deposit is situated 
approximately at N55° 24'05" latitude and W130° 29'00" 
longitude. 

Metavolcanic and metasedimentary rocks of Mesozoic 
and/or Paleozoic age are the oldest rocks exposed in the area. 
The Coast Range rocks vary in composition from diorite, 
quartz diorite. and granodiorite to quartz monzonite. These 
quartz-and sodium-rich monzonites are the sources and 
primary hosts for the molybdenum mineralization. The main 
mass of the Quartz Hill stock is a textured porphyritic quartz 
monzonite (20).' 

U.S. Borax and Chemical Co. began exploration work on 
the Coast Range intrusive complex in 1971. Several years 
of both bedrock and geochemical sampling indicated the 
presence of molybdenum in the area and resulted in the 
discovery of the Quartz Hill deposit Initial core drilling made 
in 1974-75 confirmed Quartz Hill as a molybdenum deposit. 
By the end of 1978, a total of 280 shallow and deep drill holes 
delineated at least 635 million mt of ore at 0.09 pet Mo. As 
of 1981, 70.492 m of core drilling were completed, delineating 
a total of 1.36 billion mt ore at an average grade of 0.081 
pet Mo. 

The deposit, as planned, will be mined by open-pit 
methods. Mine development will consist of removing 11.8 
million mt ore and waste rock during the first year and pro- 
cessing approximately 9.9 million mt ore. The pit will have 
an ultimate length of 3.38 km. a width of 2.09 km, and an 
average depth of 488 m. Based upon a mining rate of 54,420 
mt/d, the mine could produce 40 million lb of contained 
molybdenum in concentrate per year for about 70 yr (21). 

Colorado 

Colorado accounts for about 22 pet of all known domestic 
resources, in terms of recoverable metal. The three major 
ore bodies are Climax, Henderson, and Mount Emmons. At 
present, these deposits contain about 3.1 billion lb of 
recoverable molybdenum, with Climax and Henderson hav- 
ing a combined annual capacity estimated at more than 100 
million lb of Mo. 

All three deposits are located in the same geologic prov- 
ince, the Colorado mineral belt. Climax and Henderson are 
located close to major Tertiary faults, the Mosquito fault and 
the Berthoud Pass fault, respectively (22). The ores are 
associated with composite intrusives of nearly identical age 
and composition. Multiple intrusions and mineralizations are 
characteristics of the deposits. 



1 Italicized numbers in parentheses refer to items in the list of references 
preceding the appendix. 



Climax 

The Climax molybdenum mine is in the Robinson min- 
ing district, on the boundary between Lake and Summit 
Counties, at about N39° 22'09" latitude and VV106 10'17" 
longitude. The deposit was first discovered in 1879 and all 
early work was directed towards gold, but after several years 
of fruitless exploration, the owner sold the property. The new 
owner dug an exploratory tunnel into the Bartlett Mountain 
hoping to intercept gold veins, until it was determined the 
mountain contained the element molybdenum. 

The Climax ore body was formed by a massive Tertiary 
stockwork in Precambrian granite and schist. The well- 
mineralized, quartz-porphyry stockwork is a component of 
the intrusive complex known as the Climax Group (28). 

The ore body has an elliptical shape with a radius of 550 
m at the outer section and 340 m at the central barren core. 
The ore deposit appears arcuate with a vertical height of 
about 425 m in its greatest dimensions. The final depth has 
not yet been reached. 

Molybdenite occurs in three distinct, but overlapping ore 
bodies. The molybdenite is finely crystalline and intimately 
intergrown in, or enclosed by, quartz. The deposit also con- 
tains tungsten (as huebnerite) and tin (as cassiterite) in 
recoverable quantities. Other minor minerals are monazite, 
galena, and sphalerite. 

In 1916 during a tungsten shortage, the American Metal 
Co. began to explore and develop the property; as substitute 
for tungsten, molybdenum demand improved. The Climax 
Molybdenum Co. was formed to operate the property. 

A 227 mt/d mill began production in February 1918, but 
was forced to close in March 1919 owing to declining demand. 
The mill remained closed until August 1924 when increas- 
ing demand for the metal led to its reopening at a capacity 
of 363 mt/d (21+). Since then, production has increased to the 
current combined capacity of 54,420 mt/d from two mines, 
an underground block-caving operation and an open-pit opera- 
tion developed in 1973. 

Though it is one deposit, reserves are classed in two 
separate categories, underground and surface. The full ex- 
tent of mineralization at Climax is not fully defined. As of 
January 1983, the underground operation had an in situ 
reserve of 244.0 million mt ore, and the open-pit operation 
had reserves of 130.6 mt (25). 

Henderson 

The Henderson Mine lies in the Urad mining district in 
Clear Creek County. The deposit has location coordinates of 
N39° 46'09" and W105° 50'29". 

The Henderson ore body is near the western edge of the 
Colorado mineral belt. The molybdenite stockwork ore body 
is associated with a rhyolitic subvolcanic center commonly 
referred to as the Red Mountain complex. The complex con- 
sists of a number of chemically and mineralogically related 
intrusive rocks. The primary units of concern are the Urad 
Porphyry, Primos Porphyry, and the Henderson Granite. 

Molybdenum mineralization occurs as veinlets, as 
coatings on joints, and as disseminations. Veinlet 
molybdenite, typically 2 to 25 mm thick, accounts for the ma- 
jority of the ore. It is fine grained and mixed with gangue 
mineral, primarily quartz, pyrite, fluorite, sericite, and 



24 



potassium feldspar. The lower part of the ore body, especially 
the Henderson Granite, contains a different type of 
molybdenite veinlets which are generally larger and contain 
different gangue mineral associations. The veinlets imply 
replacements rather than open space filling (22). 

In plan, the ore body is elliptical in shape, about 915 m 
in the long axis and 700 m in the short. The thickness varies 
from 120 to 240 m, but depths to the south and east are still 
unknown. 

The Red Mountain area was first prospected in the late 
1800's because of the red rocks produced from iron staining. 
With the absence of gold and silver, little activity occurred 
until 1914, when the Primos Chemical Co. acquired the prop- 
erty and began developing the Urad mine for molybdenum. 
Production was sporadic until Climax Molybdenum Co. ac- 
quired the property in 1963 (26). 

The Henderson ore body was discovered from an ex- 
ploratory program trying to find extensions of the Urad ore 
body. This led to the discovery of the Henderson ore body 
on the other side of Red Mountain, but considerably deeper 
than the Urad ore body (27). 

The mine employs the panel-caving system, with a capaci- 
ty of 27,210 mt/d Mo ore. The mining system makes full use 
of raise boring machines, LHD'S and rubber-tired drill jum- 
bos. Henderson ore reserves have been increasing since 
discovery. The recoverable reserves as of January 1983 are 
223 mt ore at an average grade of 0.251 pet Mo. Based on 
these reserves, the mine will have a life of at least 31 yr (25). 

Mount Emmons 

The Mount Emmons deposit is in the Elk Mountain min- 
ing district, Gunnison County, with coordinates of N38° 
52'08" latitude and W107° 02'19" longitude. The mineralized 
area lies just inside the western edge of the Colorado mineral 
belt, at the juncture of the northwestern border of the belt 
and the estern edge of the Elk Mountains. Molybdenum 
mineralization also occurs in a breccia complex that outcrops 
in the Redwell Basin glacial cirque. Within the basin, pro- 
truding outcrops of a mineralized breccia pipe stand about 
33 m above the basin floor. 

Three major zones of mineralized rock were identified 
within the Redwell Basin complex: one zone containing the 
base metals lead, zinc, and copper, and two lower zones 
related to the rhyolite and granite porphyry stockworks (28). 
The major minerals in the stockworks are molybdenite and 
cassiterite. Molybdenite occurrences vary from composite 
veinlets of quartz-molybdenite-pyrite to quartz-molybdenite, 
to monomineralic molybdenite veinlets as well as 
disseminated rosettes. Huebnerite generally occurs in veinlets 
with pyrite and in some places with quartz. Where pyrite- 
huebnerite veinlets occur with molybdenite-bearing veinlets, 
the former always cut the latter. 

The Mount Emmons molybdenum deposit is about 366 
m below the surface in the south slope of Mount Emmons. 
The ore body forms a series of inverted cuplike shells posi- 
tioned above the intrusive body. The mineralized shells form 
concentric patterns with a diameter of about 702 m and an 
average thickness of about 91 m. 

Early mining in the area was for lead-silver-copper ores. 
The Keystone Mine produced these metals for many years 
until it was shut down in 1959. The Climax Molybdenum Co. 
began exploring the area for molybdenum in 1974, and a drill- 
ing program was started in 1975. 

The size of the ore body was first published in 1977 at 
81.7 million mt ore. The current recoverable resource is now 



estimated at 132.4 million mt with an average grade of 0.258 
pet Mo (25) at a cutoff grade of 0.12 pet Mo. 

Mount Emmons is a well-explored deposit, but develop- 
ment seems still very remote. Aside from the substantial 
capital investment requirements, environmental problems 
facing the project present a major obstacle. The major areas 
of concern are land disturbance (subsidence), flora and fauna 
disturbance, air and water quality, esthetic qualities, and 
sound pollution. In addition, the residents of nearby Crested 
Butte firercely oppose the development. On February 4, 1984, 
Amax Inc. announced an indefinite delay of the project (29). 



New Mexico 



Questa 



The Questa Mine is situated in the Red River mining 
district of New Mexico, with a latitude of N36°41'50" and a 
longitude of W105°29'31". 

The Questa deposit lies on the west side of the Taos 
Range, a part of the Sangre de Cristo Mountains. The range 
is underlain by Precambrian rocks and a Tertiary complex 
(Miocene) of volcanics and intrusives. The granites were the 
first instrusions into the Precambrian rocks and were fol- 
lowed by an andesite flow overlying the granite. The 
andesites are capped by a sequence of rhyolite prophyries, 
tuff, and tuff breccias. Quartz porphyry plugs, consisting of 
quartz monzonites and granites, intruded the Precambrian 
rocks. The Tertiary intrusives and volcanics are considered 
to be the sources of mineralization that occurs principally 
along the flat-lying contact between the andesite and granite 
and extends both above and below these contacts. The 
mineralization is characterized by fracture filling ranging in 
size from hairline cracks to fissures 0.6 m wide and contain- 
ing mostly quartz, pyrite, and molybdenite, with conspicuous 
amounts of fluorite, biotite, and calcite. 

The property was first located in 1916. In 1920 
Molybdenum Corporation of America (Molycorp) acquired the 
property and started production. The mine shut down in 1921 
owing to weak molybdenum demand. Mining resumed in 1923 
at a rate of 45 mt/d from an underground operation and con- 
tinued until 1956. All production was from high-grade fissure 
veins. The deposit, selectively mined, provided an average 
mill feed of about 2.4 pet Mo (30). 

Under contract with the Defense Mineral Exploration 
Association, exploration work was undertaken from 1957 to 
1960 to determine the feasibility of establishing low-grade 
surface mining. After the contract expired, Molycorp con- 
tinued the exploration work. In 1964, sufficient reserves had 
been blocked out to justify a 9,070 mt/d operation. A high 
stripping ratio forced the decision to phase out surface min- 
ing operations in 1985, the same year that the newly 
discovered ore body (Goat Hill) is planned to be fully opera- 
tional. The Goat Hill ore body is to be mined by an 
underground block-caving method. At the present in situ 
reserve of 1 13 million mt, the mines have a life of 20 yr, at 
an annual capacity of 6 million mt ore (30)). 



Idaho 



Thompson Creek 



The Thompson Creek Mine is in a metasomatized quartz 
monzonite core of the Thompson Creek granodiorite stock. 
It is located in the Bay Horse mining district of central Idaho 
(Custer County) between Thompson and Bruno Creeks at an 



25 



elevation of 1.890 to 2,680 m. In the mineralized zone are 
a large number of coarse-grained, quartz biotite, feldspar- 
muscovite veins and veinlets containing the majority of the 
molybdenum mineralization. Molybdenite is the sole ore 
mineral with a gangue of quartz, biotite. muscovite, or- 
thoclase. microcline. sericite. and pyrite. The molybdenite is 
found as veinlets. stringers, and disseminations in the altered 
zone. Most of the ore mineralization occurs in quartz-rich 
veins. Some tungsten is present, but there are no plans for 
its recovery (SI). 

The deposit was discovered in 1967 by Cyprus Explora- 
tion Co. An open pit mine. Thompson Creek began produc- 
tion in 1983. At full capacity, the mine will have an annual 
production of about 8.051.400 mt ore, containing about 18 
million lb Mo (recoverable). At this capacity, the 175.1 million 
mt ore will last for about 22 yr (38). 

White Cloud (Boulder Creek) 

The property is in the Little Boulder Creek mining 
district of central Idaho (Custer County). The deposit is within 
the Sawtooth National Recreation Area in the headwaters 
of Little Boulder Creek. The elevation of the deposit ranges 
from 2,600 m to 2.850 m along the southeastern margin of 
White Cloud Peak. 

The White Cloud deposit is a molybdenum stockwork con- 
taining molybdenum-rich quartz veinlets in a more intense- 
ly fractured zone where mineralization is confined. Minor 
amounts of mineralization are disseminated throughout the 
remainder of the rocks (33). 

The grade of mineralization is relatively uniform on the 
surface and at depth. The grade decreases away from the 
intrusive. Molybdenite is the sole ore mineral, with quartz, 
feldspar, diopside. calcite, hornblende, garnet, epidote, 
chlorite, biotite, pyrite, and arsenopyrite as gangue minerals. 
Scheelite is found throughout the deposit, but in amounts too 
small to consider economically recoverable (33). 

White Cloud Peak is an area of great scenic beauty, so 
that any mining-related activity met strong public opposition. 
This public opposition led to the creation of the Sawtooth Na- 
tional Recreation Area, which imposes severe restrictions on 
mining activities. Mine development of this property seems 
a very remote possibility. 

Available resource data on the deposit are limited and 
conflicting. Tonnage estimates range from 90 million to 229 
million mt. 



Montana 



Big Ben 



The Big Ben deposit lies in the Little Belt Mountains on the 
north slope of Poverty Ridge in Cascade County. The deposit 
is covered mostly by unpatented claims in the Lewis and 
Clark National Forest. The explored deposit is located at 
N46°5751" latitude and W110°42'43" longitude. 

The Big Ben deposit is a stockwork molybdenum deposit 
emplaced near the contact of an Eocene hypabyssal alkali 
granite stock within a Precambrian basement of gneiss and 
schist (3U). The stock is composed of four crudely zoned 
phases, which formed the cupola of an early Tertiary 
batholith. Emplacement of the batholith as laccolithic intru- 
sions has uplifted the Little Belt Mountains to form a broad 
east-west anticlinal arch (55). It is localized along a 130- to 
170-m-wide. east-northeast trending shear near the southern 
contact of granite porphyry. The shear dips about 50° south 



and defines a segment of a major fault. Higher grade por- 
tions of the deposit appear to result from overlapping of 
several mineralizing phases (Si). 

Molybdenum mineralization occurs as molybdenite in and 
along the walls of numerous intersecting quartz veinlets. The 
most prominent quartz-filled fractures trend north 20° to 80° 
east and dip steeply north and south. Higher grade 
mineralization is associated with stronger silicification. Minor 
chalcopyrite, galena, sphalerite, and fluorite are found in open 
crystal cavities. Principal gangue minerals are finely 
disseminated pyrite and quartz (36). 

The deposit was staked between 1922 and 1940 and ex- 
plored by two adits (37). In 1942, the Bureau of Mines and 
the U.S. Geological Survey made preliminary examinations 
of the property as part of the governments strategic minerals 
investigation program, to locate emergency sources of open- 
pit molybdenum. The following year, the Bureau completed 
four diamond drill holes totaling 422 m in depth. In addition, 
the Bureau channel-sampled the underground workings and 
performed metallurgical testing of the samples. 

The resource used in this availability study for the pro- 
posed mine was 107 million mt. The deposit would be mined 
by open-pit methods at a rate of 15,286 mt/d ore and 41,272 
mt/d waste for a life of 20 yr. 



Nevada 



Tonopah (Hall) 



The Tonopah molybdenum mine is located in the San An- 
tone mining district (Nye County) on lands administered by 
the Bureau of Land Management. The deposit is situated at 
approximately N38°19'23" latitude and W117°17'31" 
longitude. 

The locus of mineralization of the Tonopah deposit is the 
contact area between the intrusive quartz monzonite stock 
and the intruded rocks consisting of sericitic quartzite, quartz 
mica schist, limestone, and tuffaceous limestone. Many nar- 
row veins characterize the contact zone, which constitutes 
about 30 pet of the rock volume. Sulfides associated with vein- 
ing are concentrically zoned. Molybdenite mineralization is 
found in relative abundance, in a ring-shaped band of 
chalcopyrite farther from the stock; sphalerite and minor 
galena occur at the fringes of the sulfide depositions (38). 

In plan view, the ore body is ring shaped with a radius 
of 635 m from the center of the stock to the center of the 
molybdenum zone. It has an approximate thickness of 103 
m. Sulfide mineralization diminishes outward from the zone 
for a distance of 660 m or 1,295 m from the center of the 
stock (38). 

The pipelike stock is separated vertically into three zones. 
The upper and the middle zones are exposed in the west and 
central portion but are covered in the east by a series of 
volcanic rocks. The upper zone ranges in depth from m on 
the west to 240 m on the east. One oxidized zone, made up 
of copper minerals in quartz monzonite, constitutes the cop- 
per ore body. The upper zone must be stripped before the 
molybdenum ore body can be mined. The middle zone, lying 
immediately below the upper zone, is unoxidized and com- 
posed of chalcocite and molybdenite in quartz monzonite; it 
constitutes the main molybdenum ore body. The lower zone 

unrated from the middle zone by 120 m of barren rock. 
Approximately 90 m thick, the lower zone contains 
molybdenite in quartz monzonite. 

The San Antone district was discovered in 1 Xfi.'i, and 
there had been intermittent production of silver, lead, and 



26 



gold until 1920 (39) when mining ceased. Since then, several 
companies prospected, explored, and sampled the area, in- 
cluding the Bureau of Mines. Anaconda, which has been ex- 
ploring the area intermittently for 25 yr, acquired the pro- 
perty in 1955 (40)). Serious exploration began in 1975 when 
three drilling rigs completed 91,440 m of core from approx- 
imately 300 holes. Current resources stand at 150 million mt 
with an average grade of 0.096 pet Mo. At full mining capaci- 
ty of 7 million mt/yr, the deposit will have a productive life 
of about 22 yr (41). 

Buckingham 

The Buckingham molybdenum deposit lies in the copper 
basin area in the northeastern part of the Battle Mountain 
mining district, Lander County, at an average elevation of 
1,770 m. The deposit is located in an area of mixed private 
and Bureau of Land Management (BLM) administered lands, 
at an approximate latitude of N40°36'56" and longitude of 
W117°03'42". 

The Buckingham deposit is a calc-alkaline, molybdenum 
stockwork porphyry system with potential credits in silver, 
gold, tungsten, and copper. Molybdenite was deposited in 
quartz veins and as fracture coatings. Copper and tungsten 
appear to form a halo near the outer 0.05 pet MoS 2 and 0.10 
pet MoS 2 rock boundaries, respectively. Chalcopyrite occurs 
in quartz and quartz-molybdenite veins, while the tungsten 
occurs predominantly in pyrite veins and as fractures which 
cut molybdenite mineralization. 

No reserve-resource data have been published on the 
Buckingham deposits. Using available data and economic 
criteria, a resource tonnage of 217 million mt was calculated 
as a part of this availability evaluation. At a mining capacity 
of 20,000 mt/d ore, the mine would have a life of about 31 yr. 

B&C Springs 

The B&C Springs deposit is in the Paradise Peak min- 
ing district, Nye County. It is situated on lands administered 
by both the BLM and the U.S. Forest Service. The deposit 
has a latitude of N38°46'50" and longitude of W117°48'06". 

The deposit was first detected by an airborne 
magnetometer and induced polarization surveys, flow in 1968. 
A diamond drilling program in the area was initiated in 1969, 
when a nearly horizontal ore zone containing 0.030 to 0.075 
pet Mo was confirmed. 

The irregular ore bodies are interlayered and interbedded 
and appear concentrated within fractured carbonates. 
Molybdenite and chalcopyrite are the major ore minerals. The 
accessory sulfide minerals are pyrite, tetrahedrite, sphalerite, 
and covellite. The gangue minerals are predominantly calcite, 
dolomite, quartz and some magnetite. 

Proposed mining and beneficiation proposals are based 
on 33,641,000 mt of demonstrated resources. At the proposed 
production rate of 6,282 mt/d, which include 943 mt of dilu- 
tion, the deposit will have a mine life of about 18 yr. 

Mount Hope 

The Mount Hope molybdenum deposit is located on the 
southeast side of Mount Hope in Eureka County, in T22N, 
R21 and 52E. The deposit lies between the southern ends 
of the Roberts Mountains and the Sulphur Spring Range. 

Except for a few patented claims in the central part of 
the deposit, both surface and mineral rights of the property 
are managed by the Bureau of Land Management. Exxon 



Mineral Co., which has a lease-option on the patented claims, 
applied to purchase about 10,000 acres of Federal land in the 
general area to construct and operate the mine and process- 
ing plants. 

The Mount Hope area was discovered in 1870 and opened 
in 1886 for lead and zinc. Other compaines worked the area 
including Universal Exploration Co., which operated the mine 
for lead, cadmium, and silver from 1943 to 1947. Exxon began 
exploring the area for copper in 1978; however, in 1981, Ex- 
xon declared the area had potential for molybdenum instead 
of copper. 

Initial results of exploration indicated an inferred reserve 
of 408.2 million mt with a grade of 0.078 to 0.192 pet Mo (42). 

If the inferred resource is brought to the demonstrated 
level in the future, Exxon proposes to mine the deposit by 
open-pit method at a daily capacity of 27,210 mt ore and about 
68,000 mt waste. Based on this capacity, the deposit is 
estimated to have a minimum productive life of 41 yr. The 
capital investment to develop the deposit was estimated in 
1983 at $600 million (43). 



Washington 



Mount Tolman 



The Mount Tolman deposit lies on the Colville Indian 
Reservation, Ferry County. This explored deposit is located 
at N48°03'20" latitude and W118°43'35" longtitude in north- 
central Washington. The topography is mountainous with 
moderate to steep slopes, with elevation rising from 390 m 
at the San Poil arm of Lake Roosevelt to 1,080 m at Mount 
Tolman, 2 km to the west. 

Mount Tolman is a hydrothermal quartz stockwork 
copper-molybdenum deposit. Ore occurs mostly within a 
610-m-thick, intense quartz stockwork zone in the Mount 
Tolman granodiorite phase of the pluton. Post-ore dikes form 
an interval of waste and increase in density to the east, even- 
tually eliminating ore (4-4). 

The mineralized zone is steep-faulted down to the east 
and north by a series of northeast-and northwest-trending 
normal fault systems. Primary ore minerals are molybdenite 
and chalcopyrite. Molybdenite occurs in quartz fracture fill- 
ings and less commonly in replacement veins of quartz sericite 
and pyrite. Chalcopyrite and some galena and sphalerite oc- 
cur as discrete grains scattered irregularly within the replace- 
ment veins of quartz sericite and pyrite. Associated magnetite 
is also present (.4.4). 

The deposit is approximately 1.6 km wide, 3.2 km long, 
and 370 m thick, with a central zone containing greater than 
0.12 pet MoS 2 (U). 

No production has been recorded from the numerous 
small prospects located near Mount Tolman. In 1953, Bear 
Creek Mining Co., an exploration subsidiary of Kennecott 
Copper Co., began examining the area in detail. In 1964, a 
permit from Colville Tribes was acquired to explore and 
evaluate approximately 20,000 acres. Upon expiration of the 
exploration permit, no new lease was signed. In the spring 
of 1978, the Tribal Business Council solicited competitive bids 
from interested mining companies. Amax Inc. was selected 
and a 3-yr exploration agreement was signed on August 8, 
1978. 

Based on the 91,140 m of diamond drilling, the prospect 
has an estimated resource of 900 million mt ore, with a grade 
of 0.09 pet Cu and 0.06 pet Mo using a cutoff grade of 0.05 
pet Mo (45). In 1982, Amax Inc. abandoned the property (46). 



27 



CANADA 
British Columbia 



Endako 



The Endako Mine, the largest primary molybdenum pro- 
ducer in Canada, is located in central British Columbia at a 
latitude of N54°02'00" and a longitude of W125°07'00". The 
crest of the open-pit mine has an elevation of 1,070 m. 

The Endako deposit is within the interior system of the 
Canadian Cordillera in the Nechako Plateau (47). The deposit 
occurs in the Endako Quartz Monzonite, which is one of the 
rock types of the Composite Topley Intrusion that are in- 
truded into late Paleozoic and early Mesozoic sedimentary 
and volcanic rocks. 

The ore body is an elongated elliptical stockwork measur- 
ing 3,360 m long and 370 m wide. The east half of the ore 
body, where the open pit has been developed, has a depth 
of 3*70 m over a length of 1,830 m. The west half of the ore 
body attains a maximum depth of 150 m, adjacent to the West 
Basalt Fault. It is characterized by intense fracturing and 
veining. 

The most abundant primary minerals are molybdenite, 
pyrite, and magnetite with minor amounts of chalcopyrite 
and traces of bornite, bismuthinite, scheelite, and specularite. 
Ore minerals occur in two types of veins: in large quartz- 
molybdenite veins and in fine fracture fillings and veinlets 
in the form of a stockwork. 

The molybdenite deposit was discovered and staked in 
1927, but exploration w r ork was sporadic until 1962 when a 
diamond drilling program was initiated by R and P Metals 
Corp. Ltd. Endako Mines was incorporated in October 1962, 
at the same time when Canadian Exploration Ltd. (a sub- 
sidiary of Placer Development Ltd.) entered into an explora- 
tion agreement. Following a positive evaluation, as a result 
of the diamond drilling program and underground sampling, 
a decision to develop the property was announced in March 
1964 (47). The present demonstrated resources are estimated 
at 195 million mt ore. 

The open pit operation has an annual production of about 
10,320,000 mt ore. The ore is processed in a standard crush- 
grind-float concentrator. The final concentrate is transfer- 
red to the roasting facility located adjacent to the mill for 
conversion to Mo0 3 . 

Boss Mountain 

The molybdenum deposit is near the headwaters of 
Molybdenum Creek on the northeast slope of Takomkane 
Mountain. The deposit is north-northeast of Vancouver, BC, 
with location coordinates of X52°06'00" latitude and 
\V120'56'00' longitude (: t H). 

The Boss Mountain deposit is part of the Quesnel Trough 
containing breccia pipe bodies about 335 m in depth, 60 to 
120 m in length, and 9 to 30 m in width. Molybdenite-rich 
quartz veins surround the upper breccias. 

Molybdenite mineralization occurs in three different 
forms: U) as disseminated fine grain mineralization within 
the quartz matrix of the breccia pipes, (2) as coarse-or fine- 
grained layers in quartz stringers, and (3) as a fine-grained 
film or paint along fractures, joints, and shear planes. 

Molybdenite was first discovered on Takomkane Moun- 
tain in 1917. and in the fall of that year several hundred 
kilograms of molybdenite ore were shipped to Ottawa. In 
1930, several hand trenches were excavated on one of the 



larger quartz-molybdenite veins and on a molybdenite-bearing 
breccia. Sporadic exploration work was done in the area un- 
til 1955 when the claims were acquired by H.H. Heustis. In 
1956, Climax Molybdenum Co. Ltd. optioned the claims and 
completed over 1,000 m of diamond drilling before ter- 
minating the option in 1960. 

Noranda optioned the property in 1961. After 4 yr of ex- 
ploration and development work, production was started in 
1965 at a mill rate of 900 mt/d. Production continued until 
1972, when the mine was closed because of the depressed 
molybdenum market. The mine was reopened in early 1974. 

The ore deposit has been mined by both underground 
open stope and open-pit operations. The current remaining 
demonstrated reserve is calculated at 4.9 million mt ore. With 
a production rate of 1,832 mt/d from underground and 1,466 
mt/d from open-pit operations, the current reserve will main- 
tain a productive life of about 6 yr (4.9). 

Ores from the mine are treated in a single-product flota- 
tion concentrator. Molybdenite concentrate is the final 
marketable product. The concentrate is packaged and 
transported to Vancouver. 

Kitsault 

The Kitsault molybdenum deposit is located in northern 
British Columbia, near the Alaskan border. The mine is 
located 7 km southeast of the town of Kitsault with location 
coordinates of N55°25'00" latitude and W129°25'00" 
longitude. The deposit lies within the rugged mountain cost 
ranges, with an elevation of about 610 m. 

The Kitsault deposit is an intrusive complex composed 
of at least five separate stocks and related dikes. The first 
three intrusives were essentially barren of sulfide mineraliza- 
tion. The last two intrusives were composed of more differen- 
tiated magmas and supplied the source for molybdenite and 
other sulfides (50). 

The Kitsault property was first placed into production 
by British Columbia Molybdenum Ltd. a subsidiary of Ken- 
necott Copper Corp., in the late 1967. The open pit and mill 
were designed to operate at a rate of 5, 440 mt/d. The opera- 
tion was shut down in mid-1972 because of a depressed 
market. 

AMAX Inc. purchased the Kitsault property from Ken- 
necott in late 1972 and reopened the mine at an expanded 
capacity. Reconstruction started in May 1979 and produc- 
tion in January 1982. Due to market conditions, the mine 
again was closed in October 1982 and remains closed 
indefinitely. 

The Kitsault deposit was mined by an open pit operation 
with a design capacity of 10,886 mt/d ore. The overall strip- 
ping ratio is 1.86 to 1.00. The current demonstrated resource 
is estimated at 104.3 million mt (25). 

Ore from the mine was processed in the Kitsault concen- 
trator by crushing, grinding, and single-product flotation. 
Molybdenite concentrate was packaged and transported to 
Vancouver, BC. 

Glacier Gulch 

The Glacier Gulch molybdenum deposit is located on the 
east flank of Hudson Bay Mountain, a glaciated pile of 
Mesozoic rocks near Smithers, BC. The deposit coordinates 
are N54°49'00" latitude and W127°18'00" longitude, with an 
exploration adit driven at an elevation of about 1,066 m. 

The oldest and most widespread lithologic unit exposed 
on the Hudson Bay Mountain is the Hazelton Group, 



28 



characterized by a thick sequence of poorly layered volcanic 
and sedimentary rock of Jurassic age. In the mineralized area, 
only volcanic members of the Hazelton Group are present (51). 

The occurrence of numerous small concentric mineral 
zones is the main geologic feature of Hudson Bay Mountain. 
The Central zone is defined by the Glacier Gulch Mo-W-Cu 
mineralization. Molybdenite mineralization is confined in frac- 
ture veins and veinlets, except for minor disseminated oc- 
currences in the quartz-monzonite stock immediately beneath 
a rhyolite plug (51). 

William Yorke-Hardy and Associates first staked several 
claims over some of the molybdenite-bearing veins in Glacier 
Gulch in 1956. Later the claims were optioned and explored 
by various groups within AMAX Inc. In 1971, Climax 
Molybdenum Corp. Ltd. (an AMAX Inc. subsidiary) pur- 
chased the property. An exploration program consisting of 
3,000 m drifting and 53,900 m of core drilling has defined 
a deposit that could become an economic source of 
molybdenum in the future. The delineated resource is 
estimated at 18 million mt grading 0.21 pet Mo. 

Ajax 

The Ajax deposit is located in the Skeena mining district 
in British Columbia. The claims lie approximately 13 km 
northeast of Alice Arm with location coordinates of 
N55°35'00" and W129°24'00". 

The eastern flank of an anticlined structure is the locus 
of a belt of small intrusive bodies of Tertiary age, which are 
composed of quartz monzonite porphyry, quartz-diorite por- 
phyry, granodiorite, and associated intrusive rock types with 
which molybdenite is associated (51). The surface exposures 
of these intrusives show an elliptical shape measuring approx- 
imately 915 by 762 m, with the long axis oriented to the 
northwest. 

Molybdenite mineralization is associated with secondary 
quartz and occurs in quartz veinlets in hair line fractures, 
as stringy lenses with pyrrhotite, or as coatings along frac- 
ture surfaces. Minor amounts of molybdenite are also found 
in disseminated form associated with interlocking quartz and 
pyrorhtite within the highly siliceous and sericitized section 
of the porphyry. The majority of the molybdenite is found 
within the fine quartz veins with molybdenite concentrated 
along contact boundaries of the veinlets (52). 

Properties peripheral to the molybdenite zone were first 
prospected for lead-zinc-silver in the early part of the cen- 
tury. The presence of molybdenite mineralization reported 
in the 1927 Minister of Mines' Annual Report, prompted S.J. 
Barclay in 1965 to locate property for Newmont Mines Ltd. 
Drilling and underground exploration work done between 
1965 and 1967 indicated that the molybdenum mineraliza- 
tion zones are lens-like in form and extremely erratic in lateral 
and vertical extent. This prospect has a resource estimate 
of 418.4 million mt using 0.036 pet Mo as a cutoff grade. 

Adanac 

The Adanac deposit is located within the Atlin mining 
district in the extreme northeast portion of British Colum- 
bia, near the head of Ruby Creek Valley. The location coor- 
dinates are N59°42'30" and W133°24'00". The deposit lies at 
an elevation of 1,463 m in an open alpine valley. 

The deposit is situated within the northern edge of Mount 
Leonard Boss, and is divided by the Adera Fault into a nor- 
thern area (53). Six major and several minor rock units were 
identified in the vicinity of the deposit. 



Veins occur in all major rock types, but are most com- 
mon in the coarse granite, crowded porphyry, and porphyritic 
granite. The Adanac deposit is approximately 1,036 m long 
and 550 m thick. Molybdenite mineralization extends beyound 
these dimensions but in small amounts (54). 

The discovery claims on the Adanac deposit were staked 
by Adanac Mining and Exploration Ltd. in 1967. During 1968, 
Adanac Mining commenced an exploration program that in- 
cluded a geochemical survey and diamond drilling totaling 
1,502 m from 12 holes. In 1969, a total of 11,273 m of dia- 
mond drilling was completed from 68 holes. Kerr Addison 
Mines Ltd. optioned the property in 1970 and carried out an 
extensive exploration program. At the end of 1971, the ex- 
ploration program accomplished 19,812 m of diamond drill- 
ing, 1,219 m of rotary drilling, and 823 m of underground 
development including bulk sampling, pilot mill tests, and a 
full-scale feasibility study of the property. 

From 1972 to 1978, exploration was again conducted on 
the property by Adanac Mining, Noranda Mines Ltd., and 
Climax Molybdenum Corp. (BC) Ltd. In December 1978, 
Placer Development Ltd. and Adanac Mining and Explora- 
tion Ltd. reached an agreement to develop the deposit. In 
1979, Placer conducted additional exploration work. Placer 
terminated the option agreement in January 1983, because 
of the depressed market. 

The current minable ore reserve is estimated at 201 
million mt at an average grade of 0.059 pet Mo. The ore will 
be mined by conventional open-pit method, with an overall 
stripping ratio of 1.56 to 1.00 (54). 

Red Bird 

The Red Bird property consists of 239 claims in west- 
central British Columbia about 160 km south of Smithers. 
The deposit is situated on the eastern edge of the rugged 
Coast Range Mountain, immediately outside the west boun- 
dary of Tweede Mine Park and the Eutsuk Nature Conser- 
vancy. The location coordinates are N53°18'00" and 
W127°0r00". 

The deposit consists of three zones which are located 
within a peripheral ring around the main mass of a quartz 
monzonite porphyry pluton. This pluton is roughly elliptical 
in shape, measuring about 1,200 m north-south and 800 m 
east-west. 

The mineralized zones occur at or near the volcanic por- 
phyry contact and peripheral to the contact. Mineralization 
is restricted to the quartz monzonite porphyry. However, ex- 
ceptions do occur, especially in the southwest zone, where 
molybdenite values in excess of 0.12 pet Mo are present in 
volcanic rocks. Quartz veining, with which the molybdenite 
mineralization is associated, is most abundant within about 
45 m of the volcanic-porphyry contact. The intensity of vein- 
ing tends to decrease rapidly away from the pluton. 

The claim on the property was first staked in 1959 by 
Phelps Dodge Corp. personnel. The claim group was enlarg- 
ed in the following years. Major exploration work on the pro- 
perty, which included mapping, trenching, geophysical 
surveys, and diamond drilling, was conducted from 1963 to 
1967. During that time, 17,350 m were drilled from 70 holes. 

In 1979, Craigmont Mines Ltd. optioned the property, 
and additional exploration work was done on the deposit (56). 
From 1979 to 1980, Craigmont completed approximately 
14,000 m of diamond drilling from 53 holes. Craigmont drop- 
ped the option agreement in 1981 due to the declining 
molybdenum market. 



29 



Although mineable resources are currently not yet fully 
established, they are estimated at approximately 100 million 
mt ore. This prospect would be mined using a conventional 
open-pit method. 

Mount Thomlinson 

The Mount Thomlinson deposit is located 38 km northeast 
of Hazelton. BC. with location coordinates of N55°35'00" and 
W127°29'00'. 

Molybdenum mineralization occurs along the north- 
western contact of stock cutting argillites of the Bowser Lake 
Group. The concentration of molybdenite and chalcopyrite 
are found in a quartz vein system along the northwestern 
border of the stock. 

Molybdenite, pyrite. and a lesser amount of chalcopyrite 
occur in altered, sheared, and fractured biotite granite and 
in a tabular stockwork zone up to 100 m wide along the north- 
west contact of the stock. The mineralized zone is characteriz- 
ed by abundant leucogranite and felsite dikes that are 
crosscut by the stockwork. The richest molybdenite 
mineralization is most intimately associated with intense 
argillitic alteration. Pyrite content commonly reaches 2 to 
3 pet in the mineralized intervals. It is generally associated 
with molybdenite or chalcopyrite. 

Molybdenum showings in the area were originally stak- 
ed in 1962. and in 1963 the property was optioned, mapped, 
trenched, and sampled by Butte Lake Mining Co. Ltd. In 
1963, the property was examined and later optioned by 
Southwest Potash Corp., a subsidiary of AMAX Inc. The 
following year. Southwest Potash Corp. conducted explora- 
tion work including mapping, surveying, and drilling of 1,377 
m from five holes. A resource of 1.8 million mt ore grading 
0.108 pet Mo, centered in the southern end of the mineraliz- 
ed zone, was determined. In 1965, exploration was directed 
toward the evaluation of the northern part of the mineraliz- 
ed zone. The option was terminated in 1965, because the 
grade was considered too low. 

The published ore resource figure for the Mount Thomlin- 
son deposit is 40.8 million mt grading 0.07 pet Mo (57). 

Trout Lake 

The Trout Lake molybdenum deposit is in southeastern 
British Columbia, about 3 km from Trout Lake Village. The 
location coordinates for the Trout Lake deposit are 
N50°38W and \V117°36W. The Selkirk Mountains, where 
the deposit is located, have an elevation ranging from 700 
to 2,700 m. 

The molybdenum deposit is situated at the north end of 
the Kootenay Arc. which is a bow-shaped formation 
characterized by a belt of highly deformed, heterogeneous 
sedimentary rocks. 

The Trout Lake molybdenite stockwork deposit is one 
of a series of calc-alkaline stocks located in the Kootenay- 
Upper Arrow Lake area. Molybdenum mineralization is 
associated with several of these calc-alkaline stocks. 

Molybdenite mineralization occurs over a vertical range 
of more than 1 .000 m in two zones: the upper, smaller "A" 
zone, which outcrops; and the larger, irregular, vertically at- 
tenuated "B" zone, which is up to 300 by 200 m wide as defin- 
ed by the 0.060 pet Mo contour. Molybdenite, as fine to 
medium flakes and rosettes accompanied by pyrite and pyr- 
rhotite, is mainly present along the margins of veins in a 
quartz stockwork. Occasionally, in higher grade zones (in ex- 
cess of 0.06 pet Mo), the molybdenite is strongly disseminated 
in microfractured intrusive bodies up to 20 m wide by 200 



m long, accompanied by large veins and intense quartz 
flooding. The major control of molybdenum grades is the loca- 
tion of the schist intrusive contact; a lesser control is exerted 
by premineral faults (58). 

Geologic ore resources, as indicated by drilling, are cur- 
rently estimated at 48.7 million mt grading 0.115 pet Mo, 
within which there are several zones of higher grade material. 
Although the ore body is open at depth, no drilling has been 
done at the lower levels of the deposit. 

The proposed mining method for the Trout Lake deposit 
is underground blasthole open stoping with delayed cemented 
backfill. At present, the ore body is accessed by an adit ex- 
tending 1,372 m through waste rock and 610 m across the 
ore body at its approximate midpoint. 



MEXICO 
Sonora 
Cumobabi 

The Cumobabi ore deposits (San Judas, Transvaal, 
Transvaal West, and Molibdeno) lie on the southern end of 
the great southwest U.S. Copper-Molybdenum Province in 
La Verde mining district in the State of Sonora. The approx- 
imate coordinates are N29°50'00" and W109°58'00". The mine 
is situated in a rugged terrain with peaks rising 1,700 m above 
sealevel. 

About 60 pet of the Cumobabi area is covered by volcanic 
rock. The volcanic sequence has been intruded by a body of 
predominantly acidic nature and is sometimes covered by 
rhyolite outflows (59). Strong tectonic activity took place 
following the intrusion which formed the breccia ore bodies 
(San Judas, Transvaal Breccia, Transvaal West, and 
Molibdeno). 

The San Judas ore body is 70 m wide, 300 m deep, and 
300 m along strike. Mineralization is found in the upper level 
of the ore body which is dome-shaped and has clearly defin- 
ed the lower limit. 

The Transvaal Breccia ore body contains high copper 
values and some silver. This intensely fractured ore body is 
somewhat smaller than the San Judas, measuring 200 m in 
length, 50 m in width, and 450 m in known depth. 

The Transvaal West is a contact breccia consisting of a 
silicified, intensely fractured zone. Molybdenite mineraliza- 
tion is essentially associated with quartz and orthoclase. 

The Molibdeno Breccia resembles the Transvaal in that 
it contains high copper values in the upper layer. The cen- 
tral portion contains the highest molybdenum values. The 
mineralized body has the form of an inverted cone, with the 
base measuring 170 m by 120 m and the apex at a depth of 
300 m. 

Small-scale mining has been recorded in the Cumobabi 
area since the late 1800's. In 1966, Minera Hermosillo S.A. 
acquired several claims in the area and conducted diamond 
drilling and underground exploration which continued 
through 1970. In 1978, Minera Cumobabi S. A. de C.V. ac- 
quired the claims including the San Judas breccia, which was 
developed and mined (5.9). 

The present composite proven ore reserves, which in- 
cludes the extension of San Judas-Transvaal porphyry arid 
the two Transvaal breccias, are estimated at 17.15 million 
mt. A large inferred resource is believed to be present, but 
sufficient drilling has not yet been conducted to accurately 

hlish the total resources. 

Thf- first ore body mined was the San Judas, by conven- 



30 



tional open-pit method. The pit was designed to handle a 
capacity of 4,300 mt of ore and waste. 

Opodepe 

The Opodepe deposit is about 70 km northeast of Her- 
mosillo, the capital city of the State of Sonora. The location 
coordinates for the deposit are N29°29'00" and W110°39'00" 
at an elevation of approximately 1,000 m above sea level. 

Mineralization of economic interest at Opodepe consists 
mainly of molydbenite and secondary copper mineralization 
located on the southern flanks of Creston Hill. Accessory 
metallic minerals such as galena, sphalerite, and chalcopyrite 
were observed, but these minor occurrences are of no 
economic importance. Most of the molybdenum mineraliza- 
tion occurs as fine-to coarse-grained (0.1-to 3.0-mm) crystals. 
The main host rock is the Creston Granite, which makes up 
the bulk ( + 70 pet) of the Creston stockwork molybdenum 
deposit as presently known. 

Over 20 pet of the mineralization is in the quartz matrix. 
Here the molybdenite occurs in fine-grained flakes (0.05 to 



1 mm), at the very contact of the quartz matrix with the brec- 
cia fragment. The remaining molybdenite occurs as coarse- 
ly disseminated rosettes in short zones of massive coarse- 
grained sericite. This type of molybdenite occurrence is com- 
monly found in Creston Granite (60). 

Exploration work in the area was carried on intermit- 
tently from the 1920's until 1959, when Cia Minera Penoles 
blanketed the area with mining claims. Several other com- 
panies conducted exploration work in same area, but later 
withdrew. In 1974, AMAX Inc. decided to negotiate an ex- 
ploration contract and initiated an exploration program which 
included geological mapping and geochemistry, followed by 
diamond drilling. A total of 40 holes were drilled between 
1974 and 1979. Cia Minera Fresnillo S.A. de C.V. assumed 
management of the property in 1981. 

An indicated geologic resource was estimated at 180 
million mt grading 0.09 pet Mo. Owing to limited explora- 
tion work, the full potential of the deposit is not yet deter- 
mined. The property can probably be mined as a conventional 
open-pit operation. 






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